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Bews . — The South-east African Flora: 
and Avicennioideae. The same thing is seen in the Iridaceae, the temperate 
forms or at least the south-western Cape forms having more primitive floral 
characters than the eastern and subtropical. The Orchidaceae, with the 
exception of the Diandrae section, have also, on the whole, retained the less 
highly developed types of floral structure in the temperate representatives. 
The Gramineae have already been dealt with from the same standpoint. 
Phylogeny, therefore, does not support so definitely the deriving of the 
temperate flora from the tropical as it did in the case of the more closely 
allied subtropical. The temperate and tropical floras have probably both 
diverged in different directions from the ancestral forms. At the same time 
it is probably true, as Sinnott and Bailey maintain, that the tropical 
climate approaches more nearly that in which Angiosperms first appeared. 
Consequently the tropical flora has remained more primitive on the whole 
in its growth forms, which are usually of a woody mesophytic type with 
simple bifacial leaves. 
The herbaceous form is on the whole derivative, the shorter life cycle 
being better adapted to colder seasons and drier situations. The bulbous 
and tuberous type with underground storage has been multiplied in an 
enormous series of forms in response to grassland conditions. Capsular 
fruits and wide dispersal of seeds have tended to replace fleshy fruits and 
animal dispersal in many families. 
Various kinds of xerophytism, epiphytism, parasitism, and the aquatic 
habit are generally derivative. Leaf division is probably, on the whole, also 
derivative and relatively recent in the Angiosperms. 
Evolution in floral morphology, however, has not always been parallel 
to evolution in vegetative form. In some cases the tropical representatives 
of a group are the most primitive in flower characters, in other cases not. 
It should not be forgotten that genera, and, where possible, species also, are 
named by the systematist on floral characters. Under favourable moist, 
warm conditions the tropical flora, while retaining a fairly uniform type of 
growth form, has broken up into an immense number of new and probably 
often fairly recent floral forms, i. e. genera and species. Each of these 
is rather rigid in its requirements, and shows little plasticity, though 
germinally each type may be relatively unstable and ready to break up into 
further new forms. At any rate, tropical vegetation is, as is well known, 
exceedingly mixed and the numbers of species extraordinarily great. The 
temperate flora, on the other hand, has produced a much greater variety of 
growth form, but has a smaller, total number of species. Each type is indi- 
vidually more plastic. A succulent, for instance, will grow quite well under 
moist conditions if competition with other plants is removed, but a moist 
tropical species can endure neither low temperatures nor dry conditions. 
While it is not safe to assume that the tropical flora has produced the 
temperate or vice versa, while it is better to consider that both have diverged 
