290 
SVEDELIUS : LIFE-HISTORY OF 
It is evident that the difference between such plants and 
Enalus is not great. Vivipary also frequently occurs in a 
genus where other species, even if not viviparous, have 
seeds in which the germination commences immediately 
after reaching the ground (F. E. Lloyd, 37). One of the 
characteristics of Enalus is that the young embryos are 
dispersed directly, the plant having no seeds. These 
embryos, however, have not reached so high a degree of 
development in connection with the mother plant as in the 
Rhizophoraceæ, nor are they provided with any endosperm. 
But the cotyledon is plentifully provided with food, and the 
further development can go on directly, because the plant 
lives under conditions in a tropical sea where the period of 
vegetation is never interrupted by external influences. 
The observations made by Borzi (7) upon Inga Feuillei 
show that it is not always plants living under wet condi¬ 
tions which show the phenomenon of the embryos being 
directly dispersed, a phenomenon which is closely allied to 
the vivipary. In Inga Feuillei the young embryos are 
directly dispersed, and according to Borzi, by the aid of birds. 
But it is remarkable that these embryos are very resistent 
to drought, so it is evident that it is not necessary for them 
to develop at once. 
Comparison with other Hydrophilous Plants.— 
The hydrophilous plants were first distinguished as a 
special pollination type by Delpino. Knuth in his great 
work “ Handbuch der Blütenbiologie ” (18, I,, p. 83) has 
divided them into two groups : the Hypohydrogamics, where 
the pollination takes place below, and the Epihydrogamics 
where it takes place above the water. It is rather remark¬ 
able that, though the hydrophilous plants are very few 
in number, they yet represent so many different types 
of pollination. For even among the hypohydrogamics, 
there are several very well distinguished types. The most 
divergent among them are perhaps Zostera, Posidonia. 
