Flora of Tropical East Africa -Amaranthaceae (1985)

C. C. Townsend

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000162486
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This volume focuses on the family Amaranthaceae. They are annual or perennial herbs or subshrubs, rarely lianes and large and mainly tropical family of some 65 genera and over 1000 species, including many cosmopolitan weeds and a large number of xerophytic plants.

FLORA OF TROPICAL EAST AFRICA

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AMARANTHACEAE

C.C. TOWNSEND

H. Schinz in E. & P., Pf. ed. 2, 16C: 7–85 (1934); A. Cavaco, “Les Amaranthaceae de l’Afrique au sud du tropique du Cancer et de Madagascar”, Mém. Mus. Nat. Hist. Nat. Paris, sér. B, Botanique, t. 13 (1962)

Annual or perennial herbs or subshrubs, rarely lianes. Leaves simple, alternate or opposite, exstipulate, entire or almost so. Inflorescence a dense head, loose or spike-like thyrse, spike, raceme or panicle, basically cymose, bracteate; bracts hyaline to white or coloured, subtending 1 or more flowers. Flowers ♂ or unisexual (plants dioecious or monoecious), mostly actinomorphic, usually bibracteolate, frequently in ultimate 3-flowered cymules; lateral flowers of such cymules sometimes modified into scales, spines, bristles, hairs or hooks. Perianth uniseriate, membranous to firm and finally ± indurate, usually falling with the ripe fruit included, tepals free or somewhat fused below, frequently ± pilose or lanate, green to white or variously coloured. Stamens as many as and opposite to the petals, rarely fewer; filaments free or commonly fused into a cup at the base, sometimes almost completely fused and 5-toothed at the apex with entire or deeply lobed teeth, some occasionally without anthers, sometimes alternating with variously shaped pseudostaminodes (see note below); anthers 1–2-locular. Ovary superior, 1-locular; ovules 1-many, erect to pendulous, placentation basal; style very short to long and slender; stigmas capitate to long and filiform. Fruit an irregularly rupturing or circumscissile capsule, rarely a berry or crustaceous, usually with thin membranous walls. Seeds round to lenticular or ovoid; embryo curved or circular, surrounding the ± copious endosperm.

A large and mainly tropical family of some 65 genera and over 1000 species, including many cosmopolitan weeds and a large number of xerophytic plants; some are locally important vegetable or grain plants, or decoratives. General accounts of the family may be found by H. Schinz in E. & P. Pf., ed. 2, 16C: 7–85 (1934) and A. Cavaco, `Les Amaranthaceae de l’Afrique au sud du tropique du Cancer et de Madagascar’ in Mém. Mus. Nat. Hist. Nat. Paris, sér. B, Botanique 13 (1962).

The appendages found between the filaments in this family have been variously called staminodes or pseudostaminodes. The latter term, though cumbersome, has been preferred. The normal stamen complement in the Amaranthaceae is 5 - rarely less and never more. Thus, the intra-staminal appendages are always supernumerary to the stamens; they are not modified, sterile stamens as is understood by the term “staminode”. The term “pseudostaminode” has also been standard in the family since its use by Schinz in his accounts of the family in both editions of “Die natürlichen Pflanzenfamilien”.

Schinz divided the Amaranthaceae into two subfamilies - the Amaranthoideae (represented chiefly in the Old World) with anthers “4-facheri_i“, and the Gomphrenoideae (represented chiefly in the New World) with anthers “2-facherig”. It seems to me that Hutchinson, Families of Flowering Plants ed. 3: 545 (1973), is more correct in describing the anthers in the family as “1- or 2-locular”. Apart from this, the arrangement used by Schinz is broadly employed in the present account, the genera in the F.T.E.A. region being deployed as follows:-

Subfamily Amaranthoideae : Anthers bilocular.

Tribe Celosieae: Ovules few to numerous, very rarely solitary and then not constantly so in the species showing this character. Celosia, Hermbstaedtia.

Tribe Amarantheae: Ovules constantly solitary.

Subtribe Amaranthinae: Seed erect; radicle downwardly directed. Amaranthus, Digera, Neocentema.

Subtribe Achyranthinae: Seed pendulous; radicle upwardly directed. Sericostachys, Sericocomopsis, Centemopsis, Lopriorea, Cyathula, Allmaniopsis, Pupalia, Dasysphaera, Vo1kensinia, Aerva, Nothosaerva, Psilotrichum, Achyranthes, Centrostachys, Achyropsis, Pandiaka.

Subfamily Gomphrenoideae: Anthers unilocular.

Tribe Brayulineae: Flowers solitary or fasciculate in the leaf axils; stamens (in the E. African plant) perigynous. Guilleminea

Tribe Gomphreneae: Flowers in spikes or capitula, axillary or terminal; stamens always hypogynous.

Subtribe Froelichiinae: Stigma capitate, penicillate or depressed and shortly bilobed, never with subulate branches. Flowers never compressed. Alternanthera.

Subtribe Gomphreninae: Stigma-branches subulate or distinctly bilobed, if stigma capitate then the flowers compressed. Gomphrena, Iresine.

During the course of studies in African Amaranthaceae, pollen morphology has proved very useful in determining generic affinity, and a general pollen survey would undoubtedly shed a good deal of light on the broad classification of the family. Investigation has not yet, however, been on a sufficiently wide basis to attempt such a revised arrangement.

SIMPLE KEY TO GENERA BASED ON READILY OBSERVED CHARACTERS

This key should be used with caution. If in doubt, the second key, p. 5, based on more technical characters should be employed.

Bracteoles with a projecting dorsal keel along at least the upper part of the midrib; inflorescences subglobose or shortly cylindrical, sessile above a pair of leaves	24. Gomphrena
Bracteoles never keeled; inflorescences very rarely sessile above a pair of leaves:
Leaves alternate:
Inflorescences globose, sessile, axillary, flower parts with long, squarrose awns; low subshrub of northern Kenya	11. Allmaniopsis
Inflorescences not globose, sessile and axillary, not with long, squarrose awns:
Procumbent plant with rather succulent, spathulate-obovate leaves; very local on seashore, or shore of lakes in the coastal belt	2. Hermbstaedtia
Plant not having succulent, spathulate-obovate leaves:
Plant with all the flowers fertile, bearing stamens and/or ovary and style:
Flowers densely white-woolly:
Leaves usually obviously pilose at least on the lower surface (glabrous in some forms from Zanzibar and the coast, where Nothosaerva is not recorded)	15. Aerva
Leaves glabrous or with a few fine hairs only	16. Nothosaerva
Flowers not densely white-woolly, tepals glabrous or furnished with a few multicellular hairs towards the base:
Flowers unisexual, ♂ near the top of the inflorescence or scattered among ♀; flowers green, never tinged with white or pink and never with more than a single, central nerve	3. Amaranthus
Flowers always ♂; tepals in several species tinged with or wholly white or pink when fresh, and in several with 3 or more nerves	1. Celosia
Plant with modified sterile flowers present (frequently one on each side of a fertile flower), with the appearance of scales, spines or wings:
Each bract with a single fertile flower subtended on each side by a modified sterile flower	4. Digera
At least some bracts subtending 2–3 fertile flowers, which with the modified flowers form a burr-like fruiting unit containing 2–3 seeds	5. Neocentema
Leaves opposite, at least the majority (scattered alternate leaves and branches may sometimes occur in Psilotrichum):
Modified sterile flowers (formed of hairs, spines, bristles or scales) present, frequently one on each side of a fertile flower:
Sterile flowers of greatly elongating plumose hairs; a tall forest climber	6. Sericostachys
Sterile flowers of bristles, scales or spines, never of hairs; sometimes scrambling but not tallclimbing:
Sterile flowers of fine, straight, flexible bristles:
Leaves cordate or truncate at the base, with an abrupt, short petiole; flowers green or reddish green in life	13. Dasysphaera
Leaves shortly or long-cuneate into a long petiole; flowers (at least the stamens and style, and often the inner surface of the tepals) bright magenta	14. Volkensinia
Sterile flowers of glochidiate, hooked or straight but rigid spines:
Spines of sterile flowers straight, neither glochidiate nor hooked	10. Cyathula
Spines of sterile flowers glochidiate or uncinately hooked:
Spines of sterile flowers in 3 or more rigidly stalked clusters, stellately divergent from the top of the stalk in fruit	12. Pupalia
Spines of sterile flowers separate to the base, or meeting in a very short, weak stalk	10. Cyathula
Modified sterile flowers absent, all flowers fertile: Flowers unisexual on separate plants, minute (tepals 1–1.25 mm.), in ter...

Table of contents

• Cover
• Title Page
• Copyright Page
• Amaranthaceae
• Index to Amaranthaceae