DEVELOPMENT AND DISTRIBUTION OF THE LEGUMINOSA. 355 
The Geography of the Cretaceous and Later Periods. 
It isalways a matter of difficulty to determine the amount 
of reliance which can be placed upon geological evidence 
in the elucidation of problems dealing with the distribution 
of any particular angiospermous genus in former times. 
There are, however, several points upon which reliance 
may be placed in this inquiry, and these depend, in part, 
upon the relations of land and sea, and the general relief 
of the land, and, in part also, upon the general characters 
of any particular group of plants under consideration 
occurring in the fossil state. Thus, conclusions fairly 
definite may be reached as to the nature of the climate of 
a bygone period from a study of the plant remains as a 
whole from rocks of that age. Satisfactory results may 
also be obtained as to the order, the family, the genus, or 
even the species, to which a plant belongs, provided full 
and abundant material be available for examination. On 
the other hand it is extremely hazardous and quite unscien- 
tific to refer angiospermous forms of plants to genera, or 
even families, on the evidence of leaves alone, and this 
for the reason that the greatest systematic botanists need 
full material for the proper determination of modern plants. 
The following general notes concerning Upper Cretaceous, 
Tertiary, and modern geography may be found helpful in a 
discussion of the distribution of the Angiosperms. 
Modern geography is characterised by the presence of 
high mountains, great deserts, large continents, small 
inland seas, glaciated poles, and a strong differentiation of 
climate generally. 
Upper Cretaceous geography, on the contrary, was 
characterised by the presence of low-lying lands, by large 
epicontinental seas, by an extension of mild and genial 
climate from the tropics to the polar regions. The fossil 
plants discovered in sediments of this age suggest, more- 
over, that the climate was moist as well as mild. 
