208 BOTANICAL GAZETTE [SEPTEMBER 
CANDOLLE. Other members of the Claiborne flora may be sup- 
posed to have been distributed by fruit-eating birds. This seems 
clearly to apply to Ficus and probably to Malapoenna. 
It can be readily shown that the existing flora of peninsular 
Florida, the Bahamas, Bermuda, etc., contains a large element 
which has been derived in comparatively recent geological times 
from the south. In the case of the Bahamas and Bermuda, almost 
their entire flora has had such an origin. If, however, we study 
geographical distribution in the light of historical geology, we find 
that the main elements of these modern floras were already in 
existence in ‘the Middle Eocene, if not earlier. Experience teaches 
us that nearly all modern plant families, unless it be the most 
specialized forms like the orchids among the monocotyledons or 
the composites and their allies among the dicotyledons, were at 
some time more widely distributed than they are at present, and 
that the details of modern geographical distribution represent ina 
less degree the interchange of types between different areas than 
they do the greater or less degree of segregation of descendants 
of forms once spread ‘over much wider areas. Uniformity appears 
to have been the rule during geologic history and not the exception. 
From a study of the Claiborne flora it is evident that the main 
elements of the modern flora of tropical America reached as far 
northward in the Eocene as latitude 33 and probably much farther, 
and that in post-Eocene time they retreated southward. DALL,’ : 
from a study of the tertiary faunas of Florida, places 2 marked 
change in climate at the close of the Oligocene, and accounts for 
it by the elevation in the Florida area and the shifting to the east- 
ward of the gulf stream with an inshore southerly flowing cold 
current. : 
Thus while the strictly modern movement of the subtropical 
flora along the course of the gulf stream has been from the sou 
northward as the various coral islands of the Bahamas became 
evolved, this dispersion was preceded by a similar spread of the 
tropical flora on a much more extended scale during the early 
Tertiary. 
THE Jouns Hopkins Unversity 
ALTIMORE, Mp, 
* Dati, Trans. Wagner Inst. 3:1 549, 1550. 1903. 
