Britain's Ferns: A Field Guide to the Clubmosses, Quillworts, Horsetails and Ferns of Great Britain and Ireland 9780691190570

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Front cover: Intermediate Polypody Frontispiece: Lanceolate Spleenwort (bottom) growing with Black Spleenwort (top) Above: Bracken

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for

‘Rotten’ Robert G. Stolze, b. 1927

Associate Curator of Ferns, Field Museum, Chicago (ret.) Ferns and Fern Allies of Guatemala; Pteridophyta of Peru; Flora of Ecuador (Polypodiaceae–Dryopteridoideae–Physematieae)

Who has, on numerous occasions, shared with the author the wildlife and social life of Sherwood Forest, Brevard, North Carolina.

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Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540 In the United Kingdom: Princeton University Press, 6 Oxford Street, Woodstock, Oxfordshire OX20 1TR press.princeton.edu Requests for permission to reproduce material from this work should be sent to Permissions, Princeton University Press Copyright © 2020 by Princeton University Press Copyright in the photographs remains with the individual photographers. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publishers. British Library Cataloging-in-Publication Data is available Library of Congress Control Number 2020930978 ISBN 978-0-691-18039-7 Production and design by WILDGuides Ltd., Old Basing, Hampshire UK. Printed in Italy

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 What is a pteridophyte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 How to use this book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Pteridophyte identification Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Look-alikes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 The four groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Atypical ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

IDENTIFICATION KEYS

Clubmosses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Horsetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Quillworts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

GUIDE TO FAMILIES

Lycopodiaceae | Clubmosses; Selaginellaceae | Spikemosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Isoëtaceae | Quillworts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Equisetaceae | Horsetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Ophioglossaceae | Adder’s-tongues & Moonworts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Osmundaceae | Royal Fern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Marsileaceae | Pillwort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Hymenophyllaceae | Filmy-ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Polypodiaceae | Polypodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Pteridaceae | Maidenhair, Jersey & Parsley Ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Dennstaedtiaceae | Bracken . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Cystopteridaceae | Oak & Bladder-ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Aspleniaceae | Spleenworts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Woodsiaceae | Woodsias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Athyriaceae | Lady-ferns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Thelypteridaceae | Marsh & Beech Ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Blechnaceae | Hard-fern. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Dryopteridaceae | Shield-, Male- & Buckler-ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

THE SPECIES ACCOUNTS

Clubmosses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Quillworts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Horsetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 All-year-round pteridology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Juvenile ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 Urban ferns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Variation in pteridophytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Non-native and nuisance pteridophytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 Further reading and references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Resources and submitting records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Acknowledgements and photographic credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Index of English and scientific names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

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“The bright colours of flowers are admired by the least intellectual but the beauty of form and texture of ferns requires a higher degree of mental perception and a more cultivated intellect for its proper appreciation. Hence we regard the growing taste for the cultivation of ferns as proof of mental advancement.” Abraham Stansfield, 1802–1880, fern nurseryman of Todmorden, West Yorkshire

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Introduction This volume is not intended to be a comprehensive manual of pteridology (the study of the plants described in this book: the Pteridophyta or pteridophytes). Its main purpose is to facilitate the identification of ferns, clubmosses, quillworts and horsetails (pteridophytes), but it has lots of added extras to assist, inform and hopefully entertain today's user (Mr Stansfield, take note). The book might seem too bulky to be a comfortable pocket field guide, but is of reasonable weight for the rucksack, as long as users don’t – it would be quite understandable if they did – wish to carry a small library of WILDGuides to cover any ecological eventuality. While I have omitted much of the general biology of pteridophytes, where it helps I have provided background information and, where appropriate, inserted plenty of hints, anecdotes and in-depth information about species and groups of species, particularly those that have helped me to understand identification difficulties, such as the polypodies, buckler- and male-ferns. To facilitate full understanding of the terms listed in the glossary, general aspects of structure will be covered, while full detail of, e.g. reproductive processes, will be left to the reader to look up in botany textbooks and on the internet. An important aid to understanding is consideration of ancient and recent evolutionary events from which our modern species emerged, often involving extant related species growing far away, isolated over the millennia from their descendants both temporally and geographically. Modern biochemical techniques such as DNA sequencing have clarified and corrected many interrelationships that were less well defined until recently (see Pryer et al., 2004). Local histories illustrating how certain ferns became added to the British flora within the past several thousands of years similarly provide background knowledge that makes identification – I must be cautious here – not so much easier, rather, better appreciated and less problematical. Amazingly, fern biology tells us that some recently evolved species – for instance Polypodium interjectum and Dryopteris cambrensis – may well still, occasionally or even frequently, be synthesized in the wild. Indeed, speciation taking not millions or even thousands of years, but just a single generation, is happening in full view of those with the pteridological ability to see. Knowing how the appearance of related and ancestral foreign ferns may be reflected in British species is immensely valuable in appreciating which is which and how they might be related. For instance, the common British male-fern Dryopteris affinis is thought to be descended from a hybridization event involving our own D. oreades and the eastern D. wallichiana (which is a truly magnificent fern, easy to grow and readily available in garden centres). Comparison of all three species, parental and descendant, makes the identification of D. affinis, not to mention (albeit given more information) D. borreri, D. cambrensis and other male-ferns, less of a struggle. Features of the ancestors may be detected: shared and diluted in the descendant. Caveat: Confident identification of maleferns is likely to remain difficult, often impossible! – see the discussion of ‘WOBs’ (page 93). James Merryweather Lady-fern growing with Bluebells Hyacinthoides non-scripta

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INTRODUCTION

What is a pteridophyte? The word pteridophyte is a conflation of two Greek words φτέρη/fteri and φυτό/phyto which together mean fern-plant. Annoying people, who should perhaps be admonished with a gentle lesson in linguistics, will joke about pterodactyls. There is a distinct difference between Ptero (Pterodactyl means wing-fingers) and Pteri (‘Fteri’ in Greek, although in English pronounced ‘Teri’ with a silent ‘p’) which just means fern. It is unfortunate that early botanists were unable to separate the clubmosses, quillworts, horsetails and ferns – to us obviously very diverse plants – and grouped them all together as pteridophytes. Had they had access to knowledge of plant fossils (see Thomas, 1981) and modern DNA sequencing (see Pryer et al., 2004) they would never have attempted that because the pteridophyte groups separated evolutionarily hundreds of millions of years ago and structurally they are very diverse. So, the class Pteridophyta consists of ferns plus a veritable rag-bag of barely related botanical odds and ends, which require prior understanding and separation in the mind. For example, the clubmosses include two distinct types, Lycopodiales and Selaginellales, separated long before their heyday in the Carboniferous Period, 350 million or so years ago. Huperzia is really very different from the lycopod clubmosses with which it has been artificially associated since the early days of botany, yet we find a tantalizingly similar fossil Ateroxylon mackiei in rock laid down around 400 million years ago. Then, the ferns are obliged to include the adder’s-tongues and moonworts, which separated from ancestral proto-ferns long, long ago, and really are not at all similar or even remotely related to, say Dryopteris or Asplenium. In some respects they are not really ferns, yet for convenience we tend to consider them as such. The feature that separates the pteridophytes from later-evolved plants, such as conifers and flowering plants, is that they lack ‘modern’ flowers and seeds, reproducing and dispersing as spores. That was the norm for the earliest of land plants, back in the Devonian period 420–360 million years ago, and never went out of fashion, although nature updated the method and invented parallel improvements in conifers, flowering plants etc. Flowering plants keep their reproductive procedures in one place, on the plant, protected within their flowers. Pteridophytes, mosses and liverworts send their reproductive apparatus away from the plant, releasing onto the breeze huge numbers of lighter-than-air spores containing all the necessary reproductive parts in miniature, to find a suitable damp spot in which to continue their life cycle. The method works, so modern pteridophytes continue in the same way, albeit upgraded. Spores are usually very small (typically 30–50 µm) and resemble a fine dust in quantity. They are released by various, often explosive, mechanisms from capsules called sporangia (singular sporangium). At this point, we will avoid most of the detail, which can be learnt from standard botany textbooks. However, there are two types of spore production and release (sporulation) in pteridophytes: homospory and heterospory, which need to be considered during identification. The overwhelming majority of British pteridophytes are homosporous, producing just one sort of spore that develops on germination to bear male and female sex organs. Heterospory is the less common sporulation mechanism, occurring only in five disparate British species: the Lesser Clubmoss Selaginella selaginoides, the three quillworts Isoëtes spp. and the true fern Pillwort Pilularia globulifera. Each has separate male and female spores, keeping the 8 BK FERNS PP.indd 8

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INTRODUCTION

sexes apart until fertilization. The male spores are not as small as those of the homosporous pteridophytes and the females are large and contain a significant food supply (NB, when spelling, Selaginella and Pilularia have a single ‘l’ where one might expect two.) Pundits who know no better frequently (particularly on gardening programmes, where horsetails are reviled en bloc as pernicious weeds) refer to pteridophytes as ‘living fossils’ or describe them as ‘ancient plants’, accompanied by an unnecessary gasp of incredulity. They do the same, often and annoyingly, with the Coelacanth and Wollemi Pine. Please let us not follow the same naïve way of thinking. Modern pteridophytes are as evolved as any other contemporary organisms. Just because their ancestors diverged from their own ancestors a long time ago (and a lot longer ago than did any angiosperm) and they seem to resemble them doesn’t make them intrinsically ancient. Evolution is constantly at work and they have changed, a great deal, over the past many millions of years. By parallel reasoning, Homo sapiens is ‘living fossil’ if you associate us in the same way to our distant, semiaquatic, newt-like ancestor Acanthostega gunneri. Britain’s pteridophytes are fully up-to-date, thoroughly modern plants.

Three pteridophytes that do not look like ‘typical ferns’: LEFT TO RIGHT Wall-rue, Maidenhair Spleenwort and Adder's-tongue.

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INTRODUCTION

How to use this book

10

The Identification Keys The main identification tool provided here is a sequence of keys in which species are initially clustered by straightforward features that can be readily seen in the field with the naked eye, or hand lens in a few cases. Species are then broken up into smaller groups until there are comparisons of two or three species together with their salient identification features, which should enable a user to name the species. Each significant step of the identification process comes with text covering the relevant features and the suggested order in which these features are examined. Caveats, such as variability, hybrids and other potential pitfalls are provided, together with clear page cross-referencing to help straightforward navigation around the key and on to any related pages, such as further keys, information or the species account. If you have been put off by such keys in the past, please be patient with this one, because you should find it different, more user-friendly. This key has been constructed to help, not baffle you. Be warned: Sidestepping the keys in favour of picture matching can be hazardous, even though flipping through the illustrations may sometimes be successful once you have become familiar with the plants to be identified or they are so distinct as to be easy (e.g. Hart’s-tongue or Hard-fern). Many ferns need careful examination of detail for differentiation (e.g. the lady-, male- and buckler-ferns) and just idly scanning the pictures will often obtain the wrong answer. Many species will key out relatively easily, but several groups, particularly some of the ferns, consist of several species that seem very much alike or even, on first encounter, impossible to differentiate. That is where additional aids to identification are provided: tables, discussions, illustrated comparisons etc., where you are likely to need them. Technical terms have been kept to a minimum but a few new words, familiar to pteridologists and in common usage when they speak to one another, are best learnt. For instance, ‘indusium’ or ‘sorus’ tells you precisely and succinctly what is meant. If a term is unfamiliar you can quickly look it up in the glossary (p. 12). The first time you use the keys, start at the very beginning on p. 16. After a few goes, you will soon get used to how they work and be able to decide which parts you may skip. For instance the ferns proper begin on p. 27, so if you are confident that you have an as yet un-named fern and it’s definitely not a clubmoss, quillwort, horsetail or another sort of plant masquerading as a fern start there. Next, once you have learnt how a fern frond’s architecture works, you will know which page further into the keys you may fairly jump to as your starting point. Species Descriptions When, in the keys, you reach a species identification, you are directed to a species account (example opposite) which provides details of structure, biology, habitat etc. plus relevant illustrations. If these confirm your identification, all well and good, but if not, return to where you left the keys and back-track to try again. Classification Each pteridophyte family (recognized by the suffix ‘aceae’) is provided with its own chapter, some quite brief while others necessarily contain much detail, which will be helpful with understanding family and species characteristics. If identification difficulties are encountered, it might be advisable to review the relevant family chapter. Clarification For fern groups likely to provide difficulties (polypodies, shield-, male- and buckler-ferns), a table is provided so that comparable characteristics may be assessed side-byside as an additional aid to identification. In the case of the male-ferns, several further aids are provided, including photographic comparisons of intricate structural detail. Rewards Quite rapidly, identifications will get easier and very soon you will be confidently naming certain ferns on sight, even at apparently ridiculous distance or out of the corner of

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HOW TO USE THIS BOOK

your eye while driving along country lanes . It is so satisfying to identify a critical species of fern from far away, walk up to it, WILDGuide in hand, and discover you were right! Another source of forgivable smugness will come when you predict (or even just sense a nagging feeling) which rarity will be growing in a particular habitat and then find it . Royal Fern seems to be particularly good at providing this sort of gratification . Icons and pointers → = feature pointer; = feature area; = hand lens needed

{

English name | Scientific name Conservation status: IUCN Red List (see below)

Cross-references to further information

FERNS | SHIELD-, MALE- & BUCKLER-FERNS LC

Numbered images showing key features

FAMILY GUIDE p. 84

Borrer’s Scaly Male-fern

2

Name means: Wood fern named after William Borrer.

3

{

{

Observation tips: Dark patch on frond underside at junction of costa and rachis (see p. 236). Fronds soft and matt in shade, stiff and glossy in the open, green 1 4 (not particularly yellow). Slender rachis means that fronds arch gracefully, some of them sideways 1 →. Description/Habitat: Also see pp. 87–96, 236–241. Single crown ‘shuttlecock’ plants 1 (multiple in very mature plants) with narrow, bipinnate, ± flat fronds. The pinnules are often spread apart so that there is space between them; parallel-sided with a distinctly square apex bearing acute teeth, particularly prominent on the corners 2 (see Attachment of lowest basiscopic pinnule (p. 239)). Immature sori ( ) have their indusia tucked under the sporangia (NB may be tucked under in some Common Male-ferns D. filix-mas). As the sporangia ripen, indusia roll but do not shrivel, resembling minute chanterelle mushrooms. Stipe and rachis scales are dense, pale beige coloured 3 . Grows mostly in the shade of woodland but sometimes in the open where it can resemble Golden Scaly Male-fern D. affinis (p. 228), being glossy and yellowish, with square pinnules, which are toothed, and the indusia roll rather than split or shrivel. Distribution/Status: Widespread and common. Not threatened. Similar species: All five male-ferns require very careful diagnosis. Pinnules p. 239 | Sori p. 241 Most similar, at a distance, is Common Male-fern (p. 226).

4

Widespread and common

1

DRYOPTERIDACEAE

Male-ferns p. 86 | Key pp. 37–39 | Comparison Table p. 234

Dryopteris borreri

Woodland, moorland

J

F M A M

Rhizomes: Fronds:

J

J

A

S

O N D

compact 30–120 cm

bipinnate 2B Frond code: Winter-green: partially; fronds gradually senesce as frosted

230

231

BK FERNS V6 2.indd 230-231

Overview and description with references to numbered images

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Distribution map Form ‘at-a-glance’

Status and habitat

Phenology

taXonomic notes Taxonomy and names follow Stace (2019) except for the following: 1) Bracken (p. 164) and Pinewood Bracken (p. 166) are both treated as species . [as adopted by IUCN following Christenhusz et al. (2017) which states “but it is best treated as a separate species as they are not genetically and ecologically overlapping .”] 2) Hard-fern (p. 204) Struthiopteris spicant [Blechnum spicant in Stace] . 3) Male-ferns of the Dryopteris affinis complex (pp. 228–241) are treated here as 8 taxa (see p. 88) comprising 5 species [in line with IUCN] and 3 subspecies . [Stace (2019) recognizes Dryopteris affinis as a single species comprising 4 subspecies but acknowledges other treatments (4–8 recognized species) with the caveat that “our knowledge at present is insufficient to effect such an approach, even though that might well be desirable .”] 4) Shade Horsetail (p. 124) is used in this book; [Shady Horsetail in Stace]

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Phenology codes ■ Young frond ■ Mature frond ■ Spores ■ Dead frond

Conservation status codes A Vascular Plant Red List for England BSBI (2019) CR Critically Endangered EN Endangered VU Vulnerable NT Near Threatened LC Least Concern DD Data Deficient NE Not evaluated

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INTRODUCTION

Glossary Some of of these technical terms have not been used in this book, but will be encountered elsewhere. acroscopic   (see also basiscopic) acute adnate annular cells

of pinnules, pointing upwards, i.e. towards the apex of a frond (see p. 27)

pointed wholly or partially joined along margin; not stalked (pinna or pinnule) cells of the annulus of a sporangium (the mean numbers of these cells confirm polypodies) annulus row (‘ring’) of thick-walled cells in the wall of a sporangium antheridium; pl. antheridia male organ of non-flowering plants apex farthest point; tip apomixis; apomictic (adj.) reproduction from generative tissues without fertilization archegonium; female organ of non-flowering plants   pl. archegonia axil junction of leaf and stalk basal cells Polypodium only. The 1, 2, or 3 cells situated between the annulus and stalk of a sporangium basic; base-rich neutral to alkaline (soils) containing nutritionally significant concentrations of calcium and magnesium ions basiscopic; of pinnules, pointing downwards i.e. towards the lower parts (base) of a   (see also acroscopic) frond (see p. 27). Used in descriptions of some male- and buckler-ferns to refer to the downward-pointing pair of pinnules adjacent to the rachis. bipinnate frond divided twice calcicole; calcicolous (adj.) favouring basic, alkaline, high pH soils (especially calcareous) calcifuge favouring acidic, low pH soils (e.g. moorland) class taxonomic rank consisting of related orders complanate flattened costa midrib of a pinna crosier unfurling frond cultivar morphological variant of a species in cultivation, either descended from field collection or synthesized in the greenhouse, signified: ‘Name’, sometimes including the name of the discoverer/grower or where found (e.g. Athyrium filix-femina ‘Gemmatum Bolton’) (see variety) dehisce splitting along a line of weakness in the sporangia in order to release the spores dimorphic of two types, usually referring to fern fronds family taxonomic Rank consisting of related genera (see genus) frond fern leaf gametophyte minute reproductive phase of a pteridophyte, which bears the sex organs   (see prothallus) gemma; pl. gemmae a bud or bulbil that detaches from the main plant and develops into a new plant genus; pl. genera taxonomic rank consisting of related species gryke fissure in limestone rock heterosporous (adj.); producing separate male and female spores which germinate to produce   heterospory separate male and female gametophytes (Selaginella and Pilularia only) homosporous (adj.); producing a single spore type, male and female combined, which   homospory germinates to produce a gametophyte bearing both male and female organs

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GLOSSARY hybrid

imbricate indurated cells indusium; pl. indusia inflexed lanceolate megasporangium;   pl. megasporangia microsporangium;   pl. microsporangia order ovate paraphyses phenology photosynthesizing;   photosynthetic (adj.) pinna; pl. pinnae pinnate pinnule; pl. pinnules pinnulet; pl. pinnulets prothallus pteridophyte

the result of breeding between individuals of different (usually related) species. Usually sterile and therefore with no further reproduction, but the occasional fertile hybrid with survivability can become the evolutionary beginning of a new species (e.g. Polypodium interjectum, Dryopteris cambrensis) overlapping cells of the annulus with thickened walls protective membrane of sorus, which protects the developing sporangia projecting up (forwards) from the plane of a frond (of pinnae) long and narrow; approximately ‘spear’-shaped (of fronds and leaf blades) female sporangium containing megaspores (heterosporous pteridophytes only) male sporangium containing microspores (heterosporous pteridophytes only) taxonomic rank consisting of related families oval or long and broad; approximately ‘egg’-shaped (of fronds and leaf blades) hairs among sporangia (of the three Polypodium species, diagnostic of P. cambricum) periodic, seasonal life cycle events containing chlorophyll, therefore green

first level segment of a fern frond frond divided once second level segment of a fern frond third level segment of a fern frond the gametophyte of a fern botanical grouping that includes ferns, clubmosses, quillworts and horsetails pteridology the study of pteridophytes rachis midrib of frond, excluding the stipe reflexed projecting down (backwards) from of the plane of a frond (of pinnae) rhizome rooting stem from which fronds arise soil pH measure of acidity-alkalinity. 1–6 acidic; 7 neutral; 8–14 basic or base-rich. sorus; pl. sori the ‘dots’ on the back of a frond, aggregations of sporangia, usually protected by indusia species taxonomic rank consisting of related organisms that share common characteristics and are capable of interbreeding. Breeding outside the intra-species level usually results in a sterile hybrid (no further reproduction). Fertile hybrids can reproduce and may lead to evolution sporangium; pl. sporangia spore capsule stipe stalk, or the non-leafy part of a frond sporangium-containing ‘cones’ (clubmosses and horsetails). strobilus; pl. strobili tripinnate frond divided three times variety occasional morphological variant of a species found in the field (see cultivar), signified: Name, sometimes prefixed var. (e.g. Pseudathyrium distentifolium var. flexile).

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IDENTIFICATION

Pteridophyte identification – An introduction Introduction Because of the differences between the four pteridophyte groups, we must first decide to which of them an unknown plant belongs. This is best done by finding out about them in advance, so that we know what we are looking at, for example: is it a horsetail, clubmoss or something else? With that knowledge assimilated only subtle confusions can really get in the way and even they can be dispelled with just a little additional experience. For instance, an isolated leaf of a plantain such as Greater Plantain Plantago major and an adder’s-tongue can look similar on a casual glance, but not after critical inspection. The same sort of learning process needs to be applied – at first, for a short while – to lacy members of the families Apiaceae [Umbelliferae] (parsley or carrot family) or Asparagaceae (asparagus, agaves), after which any confusion with ferns will be dispelled through relatively superficial examination. So, if you need to, please leaf through the illustrations of the four different pteridophyte ‘formats’ to establish in your mind which is which, and what is not a pteridophyte, and any recognition problems at this level will soon evaporate. However – and this has already been warned about, and will be again, but definitely bears repetition – please do not attempt identification to species by picture matching, at least until you are thoroughly familiar with diversity within all genera. Such short cuts inevitably lead to identification errors which will not occur if the keys are navigated properly (except with perhaps the male-ferns and a few others, which in the field can present inherent limitations to identification and as such must be accepted as being unfortunate, insurmountable facts of biology). So, once we learn to differentiate the eight clubmosses (which look like nothing else, certainly not mosses), three quillworts (one of which is exceedingly rare) and eight horsetails (which, with their jointed stems are easily distinguished from other British plants) we can begin to sort out the ferns themselves. FERNS Even the ferns have a few taxa (particularly moonworts, the adder’s-tongues, Pillwort and also the invasive non-native Water Fern) which look distinctly different from the vast majority of ferns in general. The rest all have the familiar unfurling frond format, with profiles that range from undivided to many times divided, which is the factor that forms the basis of these identification keys to ferns. The keys are fundamental to accurate identifications. They consist of illustrated groupings of species with similar features, together with details of how to differentiate. In some cases, these lead to more detailed groupings, resulting in the suggestion of a name. Unlike quite a lot of identification keys, these are specifically intended to provide all users – from specialists with microscopes to interested naturalists – to reach an identification in as easy a way as possible. No attempt is made to baffle the user (some identification keys truly do that!) or make an identification entirely dependent upon subjective or seasonally available (therefore, often unavailable) characters. The main limitations to success might be hasty picture matching (just don’t do it until competent) or an individual user’s unconventional interpretation of the descriptions provided here. There is little that can be done about that, except that the keys have been tested with numerous ‘guinea pig’ users and revised again and again and, therefore, hopefully conform to most users’ way of thinking. 14 BK FERNS PP.indd 14

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LOOK-ALIKES

Look-alikes COW PARSLEY

JUNCUS RUSH

leaves arise from basal sheaths

Pillwort and quillworts are similar to grazed and/or young non-flowering Juncus rushes with near-cylindrical leaves . Rushes can be told by the brownish/pale, not spoon-shaped, bases to the Veined leaves leaves, which typically grow from a basal sheath . WATER LOBELIA

SHOREWEED

leaves solid

Two quillwort-like plants are Shoreweed Littorella uniflora which has solid (not four-channelled) leaves and Water Lobelia Lobelia dortmanna which has flat, blunt leaves . GREATER PLANTAIN

veined leaves

UPRIGHT HEDGE-PARSLEY

Some members of the parsley (or carrot) family (Apiaceae) – especially those species with more pinnate leaves (such as Cow Parsley Anthriscus sylvestris and Upright Hedge-parsley Torilis japonica) – could be, when not flowering, mistaken for fern fronds at a casual glance but have stems that are ‘V’-shaped in part and/or grooved, unlike the shallowly ‘U’- or ’C’-shaped or rounded stipe of a fern .

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Greater Plantain Plantago major is superficially similar to an adder’s-tongue, but these do not have the veined leaves of a plantain .

15

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IDENTIFICATION

Pteridophyte identification – The four groups OVERVIEW KEY

NB Not to scale and for preliminary recognition only: not intended to be used for identification

16

Clubmosses | 2 families; 8 species KEY ››➤ p. 20

Quillworts | 1 family; 3 species KEY ››➤ p. 26

Terrestrial . Densely clothed in small, plain, scale-like leaves; tufted with no conspicuous rhizome or far-ranging rhizomes, with vertical shoots often bearing cones .

Aquatic or semi-aquatic . Bunches of quill-like or rush-like leaves spreading from a small corm . Leaves of the two aquatic species are often washed up on lake shores . If not too damaged (if they are, better specimens will be not far away) they have a white spoon-shaped base within which the sporangia are, or were, located . If sectioned, leaves can be seen to have four parallel, longitudinal cavities with occasional cross walls . Several aquatic flowering plants can be mistaken for quillworts (see p. 15) but, if the base cannot be seen, they can be excluded by sectioning a leaf: they do not have the four channels, just spongy internal tissue .

scale-like leaves

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cones

spoon-like leaf bases

stem with four cavities, two with cross walls

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THE FOUR GROUPS

Horsetails | 1 family; 8 species | KEY ››➤ p. 22 Terrestrial, semi-aquatic or fully aquatic . Unique jointed stems with or without whorls of side branches; these branches may be regular, irregular, sparse or absent . jointed stems

Ferns | 14 families; 60 species KEY ››➤ p. 27 Defining ferns in general without an over-technical description is difficult . Most people have a good idea which plants are likely to be ferns and any difficulty in this may be overcome with familiarity, the facilitation of which is the purpose of this book .

Pillwort pp. 19, 144

Adder’s-tongues pp. 132–135

Moonworts pp. 59, 136

'Typical’ ferns pp. 138,150–255

Filmy-ferns pp. 142–149

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IDENTIFICATION

Pteridophyte identification – The four groups At first glance pteridophyte identification can appear daunting, but once a reader can: a) differentiate pteridophytes from other plants; and b) recognize the very different-looking four pteridophyte groups (however that is achieved) the focus can then be on evaluating the details needed to enable identification to an appropriate taxonomic level. Beyond the four ferns detailed opposite that do not fit the concept of a ‘typical fern’, start with the Overview Key on pp. 16–17. This should enable an assessment of which one of the four groups your specimen belongs to and point to the appropriate identification pathway to follow. More experienced readers may wish to skip this step and start directly with the species keys. The keys will point you, in most cases, to the species account where images and detailed text should confirm an identification. In some cases, particularly the more difficult groups, the key will take you to a more detailed, technical key before leading to a species account.

Clubmosses (pp. 98–109) OVERVIEW p. 16 | KEY p. 20 | FAMILIES p. 48

Horsetails (pp. 114–131) OVERVIEW p. 17 | KEY p. 22 | FAMILY p.  52

Quillworts (pp. 110–113) OVERVIEW p. 16 | KEY p. 26 | FAMILY p. 51

Ferns (pp. 132–255) OVERVIEW p. 17 | KEY p. 27 | FAMILIES p. 58

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THE FOUR GROUPS | ATYPICAL FERNS

Pteridophyte identification – Keys Ferns that do not look at all like other ‘typical ferns’ Killarney Fern  Vandenboschia speciosa

p. 144

Forked Spleenwort  Asplenium septentrionale

p. 190

Exists in Britain and Ireland as independent gametophytes. Even if you do stumble on this strange fern, it is most unlikely you will recognize it unless you have encountered it before and, therefore, already know its habitat and what it looks (and feels) like. See page 62 for a full introduction.

Technically, the fronds are bipinnate, but do not look so, at all. They are strap-like, randomly forked or toothed. Carefully (this fern is quite rare) turn fronds over to observe elongate sori typical of the genus Asplenium.

Pillwort  Pilularia globulifera

Water Fern  Azolla filiculoides

p. 140

Pillwort grows at the margins of ponds which dry up in summer; submerged in the shallows the rest of the year. It has a much-branched rhizome that creeps along the surface of the mud in which the plant is rooted from which plain, unadorned, 10 cm-long cylindrical green fronds unfurl in a typically fern-like way. At the base of some of the fronds there are small spherical sporocarps – the eponymous ‘pills’.

p. 272

Not native; an aggressive aquatic weed, quite common in England where it can block waterways. Each individual plant is just a few centimetres across, with minute, tightly appressed leaves and a branched stem that bears dangling roots. Leaves range from wholly green to bright pink-purple, although typically greenish with a distinct pink tinge. Plants can amass as a continuous floating ‘raft’, where, due to their pinkness, they readily stand out from other floating plants, such as duckweed.

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IDENTIFICATION KEYS

Key to Clubmosses and spikemosses IDENTIFICATION TIPS | Separate initially by size of mature plant and then by overall form (tufted or creeping (rhizomatous)) and then by plant details (leaf, cone, stem) and habitat as detailed. Beware ! | small, young plants of the larger species; form of all species can vary from examples here.

Mature plants 2–6 cm | 2 spp.

Mature plants 5–20 cm | 6 spp.

TUFTED; rhizome very short or barely noticeable

TUFTED; rhizome short or absent

terminal ‘crown’ of gemmae sporangia

in leaf axils sporangia

leaves

in leaf axils

! young plants