West Indian Flora. 309 
rainfall, that we should look for the ancestors of many forms of vegetation 
which have stamped their character on the vegetation of the continent. In 
addition, the mountains of Venezuela and Guiana, representing the southern 
part of the Antillean land extension may be considered also as a center from 
which the tropic flora has spread. This region during lower and upper Creta- 
ceous periods was severed from eastern Brazil and during that time an endemic 
tropic flora was in process of development. This flora is characterized by the 
great richness in Araceae and Orchidaceae. While separated from the south 
and also with several distinet orographic systems small areas existed which 
developed peculiar endemic forms for which this region is noted. No part of 
America has been more frequently visited by European plant importers in 
search of aroids, palms, orchids and bromeliads than this. 
Later northern South America was connected with eastern Brazil and it 
was then that the plants mentioned by BALL migrated north to Guiana, where 
they form an important element, and subsequently into Central America and 
the West Indies. The tropic element of the North American flora 
represents three distinct elements of development, viz., the subandine region, 
which according to ENGLER furnished a large contingent of species, the 
Antillean continent including Venezuela and the eastern Brazilian 
district, which subsequent to the Cretaceous period furnished a considerable 
number of migrant forms which found their way northward, while the higher 
Andes contributed many types to the higher Mexican mountains.. We are not 
in a position to clearly separate from each other the plants derived from all 
these areas, but we have proceeded far enough to discover that the Mexican, 
Central American, West Indian and Brazilian tropic floras are all connected by 
identic species of plants. If diversity has occurred, it has been through the 
isolation of areas of great physiographic difference permitting the differentiation 
of new types of plant life from old forms. This separation of land masses 
into groups by the encroachment of the sea has also separated widely distri- 
buted forms which remain as relicts in circumscribed areas, or it has led to 
the extinction of many forms once widely prevalent 
West Indian Flora. GRISEBACH') early compared statistically the flora of 
the different West Indian islands under English control and the facts discovered 
by him bear out the statement just made, that although, the Central American, 
northern South American and West Indian floras are genetically related histor- 
ically, yet sufficient time has elapsed since the disruption of the Antillean 
continent to bring about a rich endemism in the several regions. Our know- 
ledge of the West Indian flora has vastly increased since 1864, but we still 
lack sufficient data on which to make a satisfactory and complete statistic \ 
comparison of this flora with others adjacent to it. We have brought out 
some of the salient features in a preceding chapter. It only remains to say 
in this connection, that the table in GRISEBACH’s great work is helpful in 
1) GrissBacH: Geographische Verbreitung der Pflanzen Westindiens. 
