American Fern Journal 
Vol. 8 JULY-SEPTEMBER, 1918 No. 3 
The Jamaican Filmy Ferns 
FORREST SHREVE 
The students who have been working for many years 
to unravel the history of the vegetable kingdom, have 
given us a very clear and convineing body of proof 
that our terrestrial plants have developed from aquatic 
ancestors. It is doubtful if any single event in plant 
evolution is of greater importance than the emergence 
from ponds, rivers and lakes, and the development of 
characteristics which make life possible on dry land. 
We are familiar with the necessity of water for fertili- 
zation in mosses and in the prothallia of ferns, and the 
fact is very impressive when we realize that none of 
the ancestors of these plants were ever free of dependence 
upon water or films of water for this critical act in their 
life histories. The emergence of plants from the water 
to the land may have occurred more than once and in 
more than one group. However this may be, we have 
humerous cases in which members of purely terrestrial 
roups have returned to the water. All of our aquatic 
flowering plants show their terrestrial origin both in 
their relationships and in the fact that they expose their 
flowers above water, where fertilization is able to take 
Place by the complex process of pollination which, 
More than any other performance or structure, was 
the thing that made terrestrial existence possible. 
Although ferns still depend upon water as the medium 
for the transfer of sperm to egg, this act may be per- 
(No. 2 of the Journa (8: 33-64, Plate 3) was issued Aug. 6, 1915.] 
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