168 
ORIGIN OF LIFE IN AMERICA 
the Antilles is generally believed to be due to accidental dis¬ 
persal. The seeds of these plants are supposed to have been 
conveyed to southern Florida from the West Indian Islands 
by winds, ocean currents or migratory birds. Professor 
Engler,* for instance, argues that a direct land connection 
between the West Indies and North America by way of Florida 
could never have eixsted, because the latter had been sub¬ 
merged beneath the sea until the end of Tertiary times, 
and that seeds are easily conveyed to Florida by the branch 
of the Gulf Stream sweeping along the northern shore of 
Cuba in a north-eastward direction, carrying quantities of 
vegetable matter and often even tree trunks. Winds could 
only transport such seeds that are specially adapted for long 
flights. As regards migratory birds, which are popularly 
believed to carry seeds to great distances in their crops 
and among their feathers, it may be pointed out that 
the main highway for birds travelling between the eastern 
States and South America is by way of north-western 
Florida and Cuba, and not by southern Florida.f If 
birds had any special influence in the transport of seeds, not 
the southern portion of Florida but the northern one should 
show affinities in the flora with the West Indies. If the 
resemblance in the vegetation of southern Florida and the 
Antilles were mainly due to the Gulf Stream, we should expect 
to find the most pronounced similarity between the two floras 
among the strand plants of Florida. This is not the case. 
The great majority of the flowering plants now known to be 
common to the West Indies and North America occur in what 
is called the “ hummocks ” of the southern extremity of 
Florida. These hummocks consist of isolated groups of hard¬ 
wood trees, shrubs and vines, and are scattered like islands 
in the everglades and pine forests, instead of being surrounded 
by the ocean. Moreover, the flora of southern Florida is by 
no means exclusively West Indian in character. About forty 
species of plants are peculiar to southern Florida, and over 
twenty are found elsewhere only in Mexico.J 
* Engler, A., “ Entwicklungsgeschichte d. Elorengebiete,” II., p. 215. 
t Cooke, W. W., “New Facts about Migration of Birds,” p. 376. 
| Harshberger, J. W., “ Floristic Elements of Eastern North America,” 
p. 612. 
