THE CLIMATIC DISTRIBUTION OF CERTAIN TYPES OF 
ANGIOSPERM LEAVES^ 
Irving W. Bailey and Edmund W. Sinnott 
The instability of the gross or superficial characters of leaves has 
been emphasized by many taxonomists, and by a number of morpholo- 
gists who have desired to bring into the limelight the conservatism 
of internal structures. Indeed, the prevailing opinion among botan- 
ists seems to be that foliar characters, except among small groups of 
closely related species, are so unreliable as to be of Httle value in the 
study of relationship and phylogeny. The warmest supporters of the 
opposite view, as might naturally be expected, are to be found among 
those paleontologists whose attention has been focused upon the 
identification of leaf impressions. 
It occurred to the writers that a careful study of the distribution 
of various types of Angiosperm leaves in the principal phytogeograph- 
ical regions of the earth might throw some light upon the question of 
the conservatism of foliar characters and their modification by environ- 
mental factors. 
Fortunately, the task of tracing the distribution of foliar structures, 
particularly of the more conspicuous external ones, is facilitated by 
the fact that there are now available numerous published floras and 
large herbaria where descriptions of the leaves of plants from varior:3 
parts of the world can be obtained. It is to be regretted, however, 
that so many taxonomists have made their floras and collections 
representative of political rather than of phytogeographical areas, 
and that ecological notes usually are meager or entirely absent. 
In the following pages are summarized the results of an investiga- 
tion upon the leaf form of Dicotyledons, undertaken in an endeavor 
to secure more specific information in regard to the distribution of 
leaves and leaflets with entire and non-entire (Crenulate, crenate, 
serrulate, serrate, dejtticulate, dentate, lohed, incised, etc.) margins. 
^ Investigations upon the phylogeny of the Angicsperms, No. 6. 
24 
