OF CEYLON AND INDIA. 
309 
sheet, as it seems to be in the other figures. Closer exami- 
nation shows that it is really branched in an irregular 
manner, so that any small portion of it consists of ribbon- 
shaped strips, rarely more than 1 cm. wide. The actual 
growdng apices, which at this season may still often be found 
just below the water surface, are more or less fan-shaped. 
Closer inspection with a lens reveals the rosettes of small 
linear leaves which are scattered among the floral shoots and 
usually arranged in more or less regular longitudinal rows 
along the strips of thallus. The floral shoots themselves 
will be found to be at the edges and tips of the thallus 
branches ; each has one flower which emerges on a short 
pedicel from a small bristly cupule. In herbarium specimens 
the leaf -rosettes and even the cupules are often represented by 
scars or little pits. In the large specimen in PI. X. the 
cupules can be clearly seen, the fruit stalks having fallen out. 
Germination and Life History .—T'h.Q seeds are shed upon 
the rocks and upon the dead surface of the old thallus, 
where they remain until the water rises to cover them. The 
epidermal layer of cells of the testa swells up when wetted, 
like that of the seeds of Linum, &c. This has often been 
described as an adaptation to fasten the seeds to the rocks 
for germination. It is true that when it dries after wetting 
the seed is very firmly fastened to the rock, but the next 
wetting washes the seed off once more, and it does not seem 
probable that this mucilaginous coat can have anything to do 
with preparation for germination ; it seems rather to enable 
the seeds to be carried away by the feet of wading birds. 
These may often be seen walking on the thalli in the dry 
weather, and some of the minute sticky seeds must be 
carried away by them. In fact, this is almost the only 
conceivable method in which these plants can be carried 
from one river to another. The number of seeds produced 
is very large, each flower, as a rule, setting a full complement 
of about 200-250, and the whole rock being covered with 
fruits, but of all this multitude very few ever come to 
