On the Life-History of Enalus 
acoroid.es.* 
(A Contribution to the Ecology of the Hydrophilous Plants.) 
BY 
NILS SYEDELIUS.t 
(With Plate XXIV., A and B, and seven figures in the Text.) 
URING my stay in Ceylon in 1902-03 to study the 
marine algæ I had also many opportunities to make 
observations on the marine phanerogamic plants. Among 
these, the family of Hydrocharitaceæ is represented on the 
Ceylon shores by the three genera: Enalus, Thalassia, and 
Halophila, and each genus by one species. Upon the first 
mentioned of these plants, Enalus acoroides (L. fit.), Steud ., 
I shall now record some observations. 
This plant was first observed by the Indian explorer Johan 
Gerhard König “ inter insulas Zeylonicas.” According to 
a description by König it was named Stratiotes acoroides by 
the younger Linné. Afterwards the plant was separated 
by Richard as a special genus under the name of Enalus. 
That Enalus acoroides belongs to that group of hydrophi¬ 
lous plants, of which Yallisneria spiralis is the oldest known 
example, and which is characterized by the male flower 
being detached underneath the surface of the water and 
conveyed by floating to the female flower, is already evident 
in Zollinger’s notes about this plant { : “flores £ citissime 
* j E. acoroides , Aschers, and Gürke in Engl, and Prantl, Nat. Pflanzenfam. ; 
Enhalus Koenigii , Rich. 
f Written in English by the author, and the diction corrected so far as 
necessary by the Editor. 
% According to Ascherson (2), p. 176. 
[Annals of the Royal Botanic Gardens, Peradeniya, vol. II., Pt.. II., August 1904.] 
