310 Part III. Chapter 3. 
elucidating the fact that there is a greater endemism in each of the Greater 
Antillean islands than in those of the Lesser Antilles, for the simple reason 
that the large islands are continental in aspect, have sedimentary rocks and 
represent part of the original Antillean landmass, which was covered by an 
Antillean flora of great richness, while the islands of the Lesser Antilles are 
volcanic and of comparatively recent creation, representing a line of weakness 
of the earth’s crust through which volcanic material has been extruded along 
the eastern edge of the lost Atlantis (Antillean continent), when it sank out 
of sight with the formation of the American Mediterranean, the Caribbean Sea. 
The flora of these islands, therefore, is a recently derived one and represents 
one that has not had sufficient time for the differentiation of new endemic- 
types, hence the discrepancy in the number of endemic types in the two. 
groups of islands which the table of GRISEBACH sets forth. Presumably the 
appearance of the Caribbean Sea by the depression or sinking down of the 
former land surfaces of the Antillean continent to great depths below the 
surface separated the Antillean flora into three parts, viz., the West Indian, 
the Central American and the northern South American. The West Indian 
flora was at one time perhaps remarkably uniform for during the close 
the Tertiary period, we have evidences that the West Indian land are 
were much more extensive than now, and the greater Antilles were once 
continuous. With the depression of the islands in subsequent periods, th 
and the present differentiation of the flora began at this time. So that for th 
several larger islands of the Greater Antilles, we have a diversification of the 
flora which has been statistically stated in a foregoing chapter of this book. 
The Bahamas are very recent geologically speaking and their elevati 
above the sea has been placed not earlier than the late Tertiary, so f 
excellent opportunities are afforded in this group to study plant migration 
closely related to plants from these islands. The chief agents in the introdu 
and distribution of the plant population are according to BRITTON ') migra 
birds, supplemented by winds and ocean currents. Notwithstanding 
geologically short period that the Bahama islands have been above the se 
they have witnessed the evolution by mutation, or otherwise, of n ımero! 
species, there being many endemic species known and many more which 
be made known as the result of recent explorations.. We have then to 
before the glacial period with seven distinct regions with types of veg® 
‚ developed during the Cretaceous and Tertiary periods in situ, and DIES 
some extent migrated from area to area, as the relative position of the land 
a BrıtTon, N.L.: A botanical Cruise in the Bahamas. Seience new ser. XXI: 628. April 
