36 
IRVING W. BAILEY AND EDMUND W. SINNOTT 
environments? Although the leaves of woody plants in such situations 
are comparatively large, they appear to be somewhat xerophilous in 
structure. The possible necessity for the reduction of transpiration 
in even the most humid of lowland-tropical rainforests is indicated 
by the extreme effects upon foliage of even a few hours' exposure to 
the full intensity of tropical sunlight. Schimper states:^ ''Every 
visitor to the botanic gardens at Buitenzorg knows that many plants, 
during the later hours of the generally sunny forenoon, usually 
exhibit clear signs of incipient wilting; this continues to increase 
rapidly until the occurrence of the afternoon shower of rain, by which 
time many leaves hang down quite in a drooping condition, although 
they are not unprovided with contri \/ances against transpiration. 
During my visit to Buitenzorg in the midst of the rainy season, four- 
teen rainless sultry days passed in rapid succession, and the vegetation 
presented a parched appearance such as would hardly have arisen in 
Europe after a period three times that length. The air remained very 
moist throughout this dry period, and, in a less sunny chmate, the 
rich nightly dew would not have been so ineffective." 
Although the usual effect of the danger of excessive transpiration 
seems to be to produce xerophilous leaves with entire margins, there 
are a number of apparent exceptions to this rule. In the sclerophyllous 
woodlands of warm-temperate regions, the marked tendency for the 
reduction in leaf surface may result {Proteaceae, Cunoniaceae, Quercus 
ilex L., Primus ilicifolia Walp., etc.) in the development of highly 
specialized spinosely toothed, piijnatifid, or deeply divided, leathery 
leaves. Furthermore, certain of the softer leaved xerophytes, that 
are protected against excessive transpiration by hairy coverings of 
various sorts, have non-entire margins. 
Pinnatifid or deeply divided leaves, which are of comparatively 
infrequent occurrence among woody plants, are more common among 
herbs, and occur to some extent in more or less physiologically dry 
habitats. In such situations, however, they usually differ from their 
close relatives in mesophytic habitats in having fewer or no irregulari- 
ties, serrations, dentations, etc., on the margins of their lobes and 
sinuses. 
Having studied the distribution of entire and of non-entire leaves 
and leaflets in existing Dicotyledonous floras, it is desirable to examine 
6 Schimper, A. F. W. Plant Geography, p. 220, English Edition, Clarendon 
Press, Oxford, 1903. 
