SECTIONAL TRANSACTIONS.— K. 389 



Dr. I. B. Pole Evans, C.M.G. — North of the Orange River, as far as latitude 22°, 

 and west of the Drakensberg escarpment, six types of vegetation are found — desert, 

 semi-desert, desert-grassland transition, steppe, savannah and temperate rain forests. 



The characteristic plants of the desert are : Eragrostis spinosa, Arislida brevifolia, 

 Acanthosicyos horrida, Welivitschia mirabilis, Sarcocaulon Burmanni, Pachypodium 

 Tiamaquanum, Aloe dichotoma. Euphorbia gregaria and Tamarix articulata ; of the 

 semi-desert : Aristida obtusa, Aristida brevifolia, Mesemhryanthemuin spinosum, Salsola 

 Zeyheri, Zygophyllum Morgsana, jRhigozum trichotomum, Catophractes Alexandri, 

 Parkinsonia africana and Acacia giraffoe ; of the desert-grassland transition : Aristida 

 ciliata, Schmidtia kalaJiarieiisis, Schmidtia bulbosa, Anthephora pubescens, Danthonia 

 suffruiescens, Aristida uniplumis, Eragrostis pallens, Monechma incana, Citrullus 

 vulgaris and Acacia hmmaioxylon ; of the steppe : Themeda triandra, Andropogon 

 hirtiflora, A. ceresioeformis, A. schirensis, A. nardus validus, A. excavatus and Microchloa 

 altera ; of the savannah : (in the north) Acacia pallens, Combretum porphyrolepis, 

 Adanaonia digitata, Copaifera mopane and Terminalia prunioides, (in the south) 

 Burkea africana, Terminalia sericea, Pellophorum africanum, Dombeya densiflora, 

 Faurea saligna and Mimusops Zeyheri ; and of the forest : Podocarpus latifolius, 

 P. Henkelii, P. falcatus, Gurtisia fagina, Xymalos monospora and Anthocleista 

 zambesiacce. 



Although only part of this area lies within the tropics, tropical African forms are 

 to be found over the whole ; in fact, the outstanding point about the area as a whole 

 is the strongly marked invasion of the South African flora by the tropical African 

 flora. 



The flora of this area shows affinities also with the floras of tropical America, 

 tropical Asia and Madagascar. 



The endemic tropical African flora is represented in this area by such genera as : 

 Welwitschia, Encephalartos, Urelytrum, Perotis, Phseoptilon, Portulacaria, Xymalos, 

 Burkea, Cordyla, Kirkia, Triaspis, Kissenia, Rhigozum and Catophractes. The 

 Asiatic relationship is shown by the following genera : Dinebra, Gloriosa, Sansevieria, 

 Larmea, Salvadora, Caralluma, Sessamum, Pygeum, Balanites and Commiphora ; 

 while the Madagascar affinity is shown by : Hyphaene, Kniphofia, Aloe, Faurea, 

 Hexalobus, Sphedamnocarpus, Catha, Peddiea, KigeUa and Harpagophytum ; and 

 the American affinities by Olyra, Ctenium, Anthephora, Tristachya, Raphia, Anona, 

 Ocotea, Copaifera and Hermannia. 



Miss E. R. Saunders. — A CJiapter in Floral Evolution. 



The hitherto accepted view of the constitution of the pistil is based on the 

 supposition that all carpels are of one uniform type, each representing a leaf folded 

 lengthwise and inwards, bearing the ovules on the conjoined margins. 



This conception leaves many facts unexplained. It has, moreover, recently 

 been shown to be beset with difficulties and to be at variance with numerous structural 

 features which point to a diSerent explanation, as indicated below. 



This later view recognises the same processes of evolution among carpellary leaves 

 as are met with among all other plant members, viz. differentiation of form going 

 hand in hand with division of labour. In other words the outcome of these processes 

 here, as elsewhere, is not uniformity but polymorphism. 



There is overwhelming evidence that two main types of carpel have been evolved : 

 (a) the valve or hollow type which is more or less extended laterally and, if fertile, 

 bears the ovules either singly or in a single row on either margin ; (b) the consoUdated 

 type which, if fertile, produces ovules either singly or in from one to several rows 

 on each flank of the midrib. The consolidated type may show an appreciable lateral 

 extension (semi-solid or pseudo- valve form), or it may consist merelj' of a column or 

 radial plate of tissue (solid form). 



In ovaries of one carpel (e.g. Anemone, Clematis, PotentiUa, Rosa, Alisma) the 

 carpel is of valve form. 



In ovaries of more than one carpel two kinds of carpel are usually present. Among 

 exceptions to this generalisation may be cited Nandina domestica (Berberidaceae) 

 (G2, rarely 3, of the valve type), Fritillaria imperialis (G3+3, all semi-solid). In 

 the typical case one carpel type is fertile, the other sterile. Either the fertile or the 

 sterile type, or both, may develop stigmas. When both carpel types are stigma- 

 bearing the two sets of stigmas may be ahke (occasional flowers in Eschscholzia, Reseda) 

 or dissimilar (Fumaria, Parolinia, Aphyllanthes, Aspidistra, Paepalanthus). In 

 Aphyllanthes both sets are functional, but as a rule this is not the case. 



