INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS 1 5 
regions, as is shown by the abundance in such places of the Legumi- 
nosae, Proteaceae and other compound-leaved types. These families 
• may well have acquired their leaf type under a more mesophytic 
environment (where most of the transitional conditions are found 
today) and thus have been especially fitted to invade arid regions. 
Climatic Distribution of Foliar Types 
The present distribution of leaf types with reference to climate 
provides us with evidence as to the climatic conditions under which 
Angiosperms first appeared. A study of Table I shows that the 
palmate-lobed leaf is conspicuously absent from the woody plants of 
tropical regions and is developed almost entirely in such forms under 
a temperate mesophytic environment, a fact of much suggestiveness 
since we have concluded that this leaf type is the most ancient of all. 
A number of families, such as the Rosaceae and Saxifragaceae, have 
numerous palmate species in the temperate zones but are represented 
in the tropics almost entirely by pinnate forms. 
Palmately lobed leaves occur frequently among herbaceous plants 
in the tropics and, in fact, the distribution of the various leaf types 
among herbs is much the same under widely different climatic environ- 
ments. This state of affairs, which we shall see duplicated in the 
distribution of nodal types in the various regions, is probably due to 
the fact that herbs, a recent and adaptable form of vegetation, live 
, under very different circumstances from their more primitive woody 
relatives in that they can pass over adverse conditions underground 
or as seeds. Woody plants, because of their permanent aerial habit, 
are much more susceptible to climatic differences and have closer 
structural correlations with them. It was among such plants that 
the evolution of the various types of node and leaf undoubtedly took 
place. 
We have brought forward evidence that the multilacunar type of 
node is primitive and definitely associated with the various forms of 
palmate leaves; and that the more recent unilacunar type is almost 
always connected with the simple pinnate leaf. The following table 
is therefore of interest in showing the distribution, among trees, 
shrubs and herbs, of the two nodal types in various regions of the 
globe. 
It will be observed that among herbs the proportions of the two 
nodal types, like those of leaf shape, are not widely different in the 
