ENALUS ACOROIDES. 277 
parietal placentae project to the middle of the ovary and are, 
as in so many of the Hydrocharitacese (c/. Eichler, 8), split 
quite into twolamellaB. During an early stage there are rather 
large air-chambersbetweenthese, but when the embryos grow 
out they disappear as the lamellae become pressed together 
(fig. 6). It is the low specific gravity due to these and also 
some other air-chambers in the ovary that keeps the flower 
floating before the pollination. Afterwards when the fruit 
Pig. 7.—Ovrrfe <35 x l). 
is drawn down by the spiral rolling up of the pedicel, the 
air-chambers between the split placentae disappear. 
(19) 
8(10)04 
