Euphorbia in Southern Africa: Volume 2 3030493989, 9783030493981

This book presents a new account of Euphorbia in southern Africa. Euphorbia is the second largest genus of plants in the

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Table of contents :
Contents
3: Euphorbia subg. Chamaesyce
3.1 Sect. Anisophyllum
3.1.1 Subsect. Hypericifoliae
3.2 Sect. Articulofruticosae
3.3 Sect. Espinosae
3.4 Sect. Frondosae
3.5 Sect. Gueinziae
3.6 Sect. Tenellae
4: Euphorbia subg. Esula
4.1 Sect. Aphyllis
4.1.1 Subsect. Africanae
4.2 Sect. Esula
5: Euphorbia subg. Euphorbia
5.1 Sect. Euphorbia
5.2 Sect. Monadenium
5.3 Sect. Tirucalli
6: Addenda
6.1 Names of Uncertain Application or Excluded from Euphorbia and Naturally Occurring Hybrids
6.1.1 Names of Uncertain Application or Excluded from Euphorbia
6.1.2 Naturally Occurring Hybrids
6.2 The Species of Sect. Euphorbia and Sect. Monadenium in Moçambique
6.2.1 Sect. Euphorbia
6.2.2 Sect. Monadenium
References
Name Index
Subject Index
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Peter V. Bruyns

Euphorbia in Southern Africa

Volume 2

Euphorbia in Southern Africa

Peter V. Bruyns

Euphorbia in Southern Africa Volume 2

Peter V. Bruyns University of Cape Town Rondebosch, South Africa

ISBN 978-3-030-49398-1    ISBN 978-3-030-49399-8 (eBook) https://doi.org/10.1007/978-3-030-49399-8 © Springer Nature Switzerland AG 2022 This work is subject to copyright. The Author has marked certain illustrations in the manuscript in the figure legends as follows: ‘© PVB’. whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the author give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Contents

Volume 2 3 Euphorbia subg. Chamaesyce�����������������������������������������������������������������������������������  475 3.1 Sect. Anisophyllum �������������������������������������������������������������������������������������������   477 3.1.1 Subsect. Hypericifoliae �������������������������������������������������������������������������  477 3.2 Sect. Articulofruticosae�������������������������������������������������������������������������������������   482 3.3 Sect. Espinosae �������������������������������������������������������������������������������������������������   559 3.4 Sect. Frondosae �������������������������������������������������������������������������������������������������   569 3.5 Sect. Gueinziae �������������������������������������������������������������������������������������������������   577 3.6 Sect. Tenellae�����������������������������������������������������������������������������������������������������   581 4 Euphorbia subg. Esula ���������������������������������������������������������������������������������������������  589 4.1 Sect. Aphyllis�����������������������������������������������������������������������������������������������������   591 4.1.1 Subsect. Africanae���������������������������������������������������������������������������������  591 4.2 Sect. Esula���������������������������������������������������������������������������������������������������������   607 5 Euphorbia subg. Euphorbia�������������������������������������������������������������������������������������  639 5.1 Sect. Euphorbia �������������������������������������������������������������������������������������������������   641 5.2 Sect. Monadenium���������������������������������������������������������������������������������������������   863 5.3 Sect. Tirucalli�����������������������������������������������������������������������������������������������������   868 6 Addenda���������������������������������������������������������������������������������������������������������������������  893 6.1 Names of Uncertain Application or Excluded from Euphorbia and Naturally Occurring Hybrids�����������������������������������������������������������������������   893 6.1.1 Names of Uncertain Application or Excluded from Euphorbia�������������  893 6.1.2 Naturally Occurring Hybrids�����������������������������������������������������������������  894 6.2 The Species of Sect. Euphorbia and Sect. Monadenium in Moçambique �������������������������������������������������������������������������������������������������   897 6.2.1 Sect. Euphorbia �������������������������������������������������������������������������������������  899 6.2.2 Sect. Monadenium���������������������������������������������������������������������������������  957 References �������������������������������������������������������������������������������������������������������������������������  965 Name Index�����������������������������������������������������������������������������������������������������������������������  973 Subject Index���������������������������������������������������������������������������������������������������������������������  977

v

New synonyms  published in this work: Euphorbia grandialata R.A. Dyer is reduced to synonymy under E. grandicornis A. Blanc, E. halipedicola L.C. Leach under E. bougheyi L.C. Leach, E. decliviticola L.C. Leach under E. graniticola L.C. Leach, E. stenocaulis Bruyns under E. plenispina S. Carter. Lectotypes are designated here for Euphorbia benguelensis Pax, E. caerulescens Haw., E. cucumerina Willd., E. enopla Boiss., E. fleckii Pax, E. genistoides var. leiocarpa Boiss., E. genistoides var. major Boiss., E. grandicornis K.I. Goebel, E. grandicornis J.E. Weiss, E. involucrata var. megastegia Boiss., E. latimammillaris Croizat, E. melanosticta E. Mey. ex Boiss., E. nodosa N.E. Br., E. platymammillaris Croizat, E. polygonata G. Lodd., E. proteifolia Boiss., E. trichadenia var. gibbsiae N.E. Br. and Tithymalus zeyheri Klotzsch & Garcke. A type is also designated for the genus Tirucalia Raf.

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Euphorbia subg. Chamaesyce

Euphorbia subg. Chamaesyce Raf., Amer. Monthly Mag. & Crit. Rev. 2: 119 (1817). Type (Wheeler 1939): Euphorbia supina Raf. (= Euphorbia maculata L.) Chamaesyce Gray (see under sect. Anisophyllum). Bisexual (sometimes unisexual), annual herbs, succulent shrubs with slender cylindrical stem and branches (rarely with spines developing from tips of branches), rarely geophytes or small trees. Leaves alternate or opposite, ovate to lanceolate and sometimes reduced to minute caducous rudiments, rarely arising on raised tubercles (these irregularly arranged along branches); small stipules often present and glandular or filiform. Synflorescences in axils of leaves towards apices of stem and branches or terminal on peduncle, peduncles usually simple, often with alternating or opposite bracts often differently shaped from leaves and sometimes larger just beneath cyathium, further peduncles with terminal cyathia rarely developing from axils of uppermost bracts.

Cyathia bisexual or unisexual (then males larger than females); glands 4–5, usually elliptic and flat with entire, crenulate or few-toothed outer margins, sometimes with petaloid appendages; male florets with glabrous or pubescent pedicels. Capsule obtusely 3-lobed, smooth, glabrous to pubescent, 2–10  mm diam., sessile to exserted, dehiscing explosively. Seeds 3 per capsule, 4-angled to ellipsoidal or oblong, smooth to tuberculate, with or without caruncle. Of the 16 sections (15 recognized by Yang et al. (2012), with one added by Tian et  al. (2018)), only six are represented naturally in southern Africa and most of them have only a few species in the region (see Fig. 3.1). These range from small, prostrate annuals to shrubby succulents and small deciduous trees (Table 3.1). Euphorbia heterophylla L. of sect. Poinsettia (with a single, cupped gland on each cyathium and native to the Americas) is an occasional weed in the northern parts of Botswana and South Africa.

Key to the sections of subg. Chamaesyce in southern Africa: 1. Annuals or non-succulent (non-geophytic) ephemerals usually with aborting main axis, cyathia 1–2.2 mm diam., glands often 4 and frequently with entire white or pink petaloid appendages on outer margins....................................................2. 1. Plant not ephemeral (geophytes or succulent to woody shrubs or small trees), cyathia > 2.5 mm diam, glands (4) 5 and without petaloid appendages................................................................................................................................................3. 2. Seeds with caruncle.......................................................................................................................................... sect. Tenellae 2. Seeds without caruncle........................................................................................................................... sect. Anisophyllum 3. Plant a unisexual geophyte, above-ground branches and leaves deciduous...................................................sect. Gueinziae 3. Plant not geophytic, with perennial above-ground branches, woody with deciduous leaves or succulent and sometimes with very reduced and ephemeral leaves, plant unisexual or cyathia bisexual....................................................................4. 4. Woody shrub to small tree with shiny peeling bark on trunk or towards bases of branches (lacking green branches), cyathia bisexual, seeds with caruncle,..........................................................................................sect. Espinosae 4. Shrubby to dwarf succulent with fleshy green stem and branches without peeling bark, plant unisexual or cyathia bisexual, seeds without caruncle.............................................................................................................................5. 5. Plant mostly unisexual, branches not tuberculate, frequently slender and cylindrical, leaves usually opposite and sometimes with small globular stipules, cyathial glands usually 5, with entire margins...............................sect. Articulofruticosae 5. Plant and most cyathia bisexual, branches with scattered to densely distributed tubercles, stipules minute and ± linear, cyathial glands often 4, bilobed or with wavy outer margins.......................................................................sect. Frondosae © The Author, under exclusive license to Springer Nature Switzerland AG 2022 P. V. Bruyns, Euphorbia in Southern Africa, https://doi.org/10.1007/978-3-030-49399-8_1

475

476

3 

Euphorbia subg. Chamaesyce

Fig. 3.1.  Relationships between southern African members of subg. Chamaesyce. The sections represented in southern Africa are red (those not represented are green). The length of the vertical side of each of the triangles is proportional to the number of species in that section (adapted from Yang et al. 2012).

3.1 Sect. Anisophyllum

477

Table 3.1.  The sections and subsections of Euphorbia subg. Chamaesyce occurring naturally in southern Africa.

Section Articulofruticosae Espinosae Frondosae Tenellae Gueinziae Anisophyllum

Sub-­section

Hypericifoliae

3.1

South Namibia Africa (endemic) (endemic) 10 (2) 13 (5) 2 (0) 2 (0) 2 (1) 1 (0) 2 (0) 2 (0) 0 (0) 1 (0) 4 (2) 3 (1) 4 (2) 3 (1)

Southern Africa (endemic) 16 (15) 2 (0) 2 (1) 2 (1) 1 (1) 11 (3) 11 (3)

Sect. Anisophyllum

Euphorbia sect. Anisophyllum Roep. in Duby, Bot. Gall., ed. 2, 1: 412 (1828). Anisophyllum Haw., Syn. Pl. Succ.: 159 (1812), nom. illegit., non Jacq. (1763). Chamaesyce Gray, Nat. Arr. Brit. Pl. 2: 260 (1821). Euphorbia subg. Chamaesyce (Gray) Caesalp. ex. Rchb., Deut. Bot. Herb.Buch.: 193 (1841), nom. illegit., non Raf. (1817). Type (Wheeler 1941): Euphorbia peplis L. The 368 species of this section were split into two subsections, one with three species found only in America and the other, subsect. Hypericifoliae, containing the remaining 365 species (Yang et  al. 2012), of which 11 occur naturally in southern Africa.

3.1.1 Subsect. Hypericifoliae Euphorbia subsect. Hypericifoliae Boiss. in DC., Prodr.15 (2): 20 (1862). Type: Euphorbia hypericifolia L. Bisexual non-succulent annual or perennial herbs, with short and soon aborting stem bearing fibrous roots and growth continuing from dichotomously forking branches arising in axils of few leaves on stem. Branches prostrate to ascending or erect. Leaves to 30  mm long, opposite, orbicular-­ovate and sometimes asymmetrically rounded at base, usually sessile, stipules filamentous or absent.

Perennial, nonsucculent Elsewhere (total) Annuals herbs 1 (16) 0 0 2 (2) 0 0 6 (7) 0 0 3 (4) 2 0 0 (1) 0 0 362 (365) 8 3 362 (365) 8 3

Woody shrub to tree 0 2 0 0 0 0 0

Succulents 16 0 2 0 0 0 0

Geophytes 0 0 0 0 1 0 0

Synflorescences many, each a solitary bisexual cyathium terminating branchlets, sometimes branchlet then forking around it, with minute sessile bracts, glands 4 (5), entire, green, with pale petaloid appendages along outer margins. Capsule 2–3 mm diam., exserted on decurved and later erect pedicel. Seeds minutely tuberculate or ridged to wrinkled, ± 4-angled, without caruncle. This subsection has 365 species. Most species are found in the Americas and it is poorly represented in Africa as a whole and in southern Africa too, where 11 have been recorded. These are E. chamaesycoides B.Nord., E. eylesii Rendle, E. inaequilatera Sond., E. livida E.Mey. ex Boiss., E. mossambicensis (Klotzsch & Garcke) Boiss., E. neopolycnemoides Pax & K.Hoffm., E. pergracilis P.G.Mey., E. rubriflora N.E.Br., E. schlechteri Pax, E. tettensis Klotzsch and E. zambesiana Benth. Several cosmopolitan weeds such as E. prostrata and E. hirta are also common in southern Africa. Apart from E. chamaesycoides and E. pergracilis from Namibia, most of the southern African species occur on the moister eastern side of the subcontinent. A key to the species is presented below. To give an idea of how the species look, photographs of the very widespread E. inaequilatera and an unnamed species (perhaps E. lupatensis) from northern Botswana are shown. The distributions of E. livida (endemic and restricted to the Eastern Cape and Kwazulu-­ Natal of South Africa) and E. neopolycnemoides (widespread, also known in Moçambique and Zimbabwe) are also shown (in Figs. 3.2 and 3.3).

478

Fig. 3.2.  Distribution of Euphorbia livida (© PVB).

Fig. 3.3.  Distribution of Euphorbia neopolycnemoides (© PVB).

3 

Euphorbia subg. Chamaesyce

3.1 Sect. Anisophyllum

Note: Euphorbia austro-occidentalis Thell. was included in Bruyns (2012) as if it occurred naturally in Namibia. There are two problems with this. Firstly, Meyer (1967) placed it in synonymy under E. forskalii Gay along with E. aegyptiaca Boiss. There are no grounds for questioning Meyer’s treatment of it. This is especially since Brown (1911: 508) included several of the collections listed by Thellung (1916) for E. austro-occidentalis under E. aegyptiaca. Secondly, Thellung said that it agreed in most features with E. forskalii, except for some minute details of the stip-

Fig. 3.4.  Euphorbia inaequilatera, prostrate herb ± 15 cm diam., southern outskirts of Zeerust, South Africa, Feb. 2019 (© PVB).

Fig. 3.5.  Euphorbia inaequilatera, ± 7 cm diam., hills south of Kuruman, South Africa, Feb. 2019 (© PVB).

479

ules. Thirdly, there is no evidence that it occurs naturally in Namibia, since E. forskalii is a very widespread weed and Dinter mentioned on some of his specimens that it was a weed of cultivated land. This species is therefore not included in the key below. Several species of this section are common weeds in disturbed areas in southern Africa. These include E. maculata (which occurs naturally in the Americas), E. prostrata (native to tropical America) and E. hirta (Africa to India) and they are not included in the key that follows.

480

3 

Euphorbia subg. Chamaesyce

Fig. 3.6.  Euphorbia inaequilatera, flowering, hills south of Kuruman, South Africa, Feb. 2019 (© PVB).

Fig. 3.7.  Euphorbia inaequilatera, flowering, hills south of Kuruman, South Africa, Feb. 2019 (© PVB). Fig. 3.9.  Euphorbia maculata, leaves ± 6 mm long, in crevices in a driveway in Cape Town, South Africa, Dec. 2019 (© PVB).

Fig. 3.8.  Euphorbia inaequilatera, fruiting, Matsap Pan, Postmasburg, South Africa, Mar. 2016 (© PVB).

3.1 Sect. Anisophyllum

481

Key to the species of subsect. Hypericifoliae that occur naturally in southern Africa 1. Annuals to short-lived perennials with slender fibrous roots, occasionally with main root to ± 4 mm thic.........................2. 1. Perennials with a woody rootstock 5–10 mm thick from which fibrous roots arise.............................................................9. 2. Cyathia grouped closely together in densely leafy cymes....................................................................................E. tettensis 2. Cyathia laxly grouped or solitary...........................................................................................................................................3. 3. Branches pubescent on their upper surface ............................................................................................E. mossambicensis 3. Branches glabrous except possibly near base.......................................................................................................................4. 4. Margins of leaves finely to boldly toothed..................................................................................................E. inaequilatera 4. Margins of leaves entire.......................................................................................................................................................5. 5. Plant prostrate, leaves mostly at least 5 mm broad, leathery to slightly fleshy.........................................................E. livida 5. Plant to 0.4 m tall with ascending to erect branches, leaves mostly 3–4 (7) mm broad, mostly herbaceous or only slightly leathery...................................................................................................................................................................6. 6. Petaloid appendages on two cyathial glands longer than other two...................................................................................7. 6. Petaloid appendages on all 4 (5) cyathial glands ± equal in length.......................................................................................8. 7. Stipules linear and entire, 0.5–1.5 mm long............................................................................................................E. eylesii 7. Stipules ± 0.5 mm long, divided above broad base into 3–5 linear teeth............................................E. neopolycnemoides 8. Stipules short and shortly ciliate, petaloid appendages on cyathial glands ± equalling glands.......................E. pergracilis 8. Stipules divided into 2–4 lanceolate-subulate lobules, petaloid appendages on cyathial glands narrow and rim-like on glands.................................................................................................................................................E. chamaesycoides 9. Petaloid appendages on cyathial glands forming inconspicuous narrow white margin on glands................E. schlechteri 9. Petaloid appendages on cyathial glands conspicuous, often pink or red............................................................................10. 10. Leaves with minute point at apex, cyathia borne on peduncle 1–25 mm long, petaloid appendages on cyathial glands all ± equal in size...............................................................................................................................................E. zambesiana 10. Leaves rounded at apex, cyathia ± sessile (on peduncle ± 0.5 mm long), petaloid appendages on two cyathial glands next to pedicel of exserted capsule longer than others............................................................................................E. rubriflora

Fig. 3.10.  Euphorbia lupatensis?, ± 15 cm across, north of Pandamatenga, Botswana, Feb. 2019 (© PVB).

3 

482

Euphorbia subg. Chamaesyce

Fig. 3.11.  Euphorbia lupatensis?, north of Pandamatenga, Botswana, Feb. 2019 (© PVB).

3.2

Sect. Articulofruticosae

Euphorbia sect. Articulofruticosae Bruyns, Taxon 55: 416 (2006). Type: Euphorbia aequoris N.E.Br. (= Euphorbia juttae Dinter). Mostly unisexual, succulent shrubs or dwarf succulents often dichotomously branched. Branches cylindrical or slightly longitudinally ridged, grey-green to dark green (to brown towards bases), apices drying into spines in E. spinea. Leaves rudimentary and caducous, rarely more than 5  mm long, opposite, without petiole, occasionally with small globular stipules. Synflorescences often many, each a uni-

sexual (occasionally bisexual) cyathium terminating shoot with cymes sometimes branching repeatedly, surrounded by bracts slightly shorter than leaves, glands 5, entire, often yellow-green, without appendages. Capsule 6  mm (6−8  mm) diam., capsules strongly 3-angled with somewhat flattened sides, 8−10 mm diam..................................................E. confinalis 17. Leaf-rudiments ± ovate, cyathia usually