310 WILLIS : MORPHOLOGY OF THE PODOSTEMACEÆ 
anything. Many are washed away by the water, and only 
those which are retained by a crack or crevice in the rock or 
the old thallus seem to have any chance of germinating where 
they fall. Once carried off by the stream, there is little 
chance of a seed reaching a place where it can grow. It must 
have a rocky substratum, in a rapid stream of water, and it has 
no adaptation of its own, other than small size, to enable it 
to retain a position in such a place. 
Germination, as a rule, occurs when the water rises with 
the rains of the little monsoon ; I have found seedlings in 
the period of low water in May between the little and big 
monsoons. In India the germination must evidently be later 
the further north the locality. 
The early stages are extremely hard to find in this species 
and I have only been successful in getting a very few. It is 
no easy matter in working with these plants to determine 
which seedlings belong to which species, and two consecutive 
years of observation were needed to settle these points. 
The seedlings are excessively small, and can only be obtained 
when the water-level is low, an unusual occurrence at the time 
of year when germination occurs, except just for a short 
period between the two monsoons. I have frequently 
obtained them, however, by groping in deep water for 
capsules which I knew to be those of the species sought; 
every now and then a seed will be found to have germinated 
inside the persistent capsule-valve. The seed is exalbumi- 
nous ; the hypocotyl is short and stout, and the cotyledons 
are flat when expanded, but crumpled in the embryo (PI. IX., 
4). When wetted the seed presently swells and bursts the 
testa, the hypocotyl bends down at once to the rock, and 
immediately becomes attached to it by a copious development 
of rhizoids from the superficial cells (IX., 4); these organs are 
unicellular, and flatten themselves out at the tips against the 
rock, just like those of the thallus of Tristicha. At this 
stage the seedling is extremely small, about 0.5 mm. high. 
The base of the hypocotyl now begins to expand and forms 
a larger surface of attachment, fastened by more rhizoids. 
