OF CEYLON AND INDIA. 
323 
meanwhile opened its flowers and ripened its seeds. Any 
growing point, however, that lies near the lower side of the 
plant will now tend to grow downwards along the rock, and 
may succeed in growing downwards faster than the water 
falls, so that the plant may thus survive the dry season with 
its original growing points. Oftener, perhaps, this survival 
is by means of new apices, formed from exposed thallus 
at a time when a shower has caused a temporary rise of the 
water and so covered again part of the old thallus. Especially 
may this be seen in April, when the water reaches its lowest 
and then rises again vdth the rains of the little monsoon. 
Great numbers of young plants may then be seen, which 
are easily mistaken for seedlings. Closer examination, 
however, shows them to be formed from the old thalli 
rejuvenescing in the newly submerged portions."*^ Often 
new growing points may be seen on portions of thallus 
bearing ripe fruits. Later in the season these young plants 
are still more like seedlings, as the dead portions of the 
thallus are now decayed and removed, so that nothing 
remains but the star-like plant formed by the branching 
of the new growing point, and closely resembling a seedling. 
Physiology . — A few notes on certain physiological features 
exhibited by these plants must now be given. A general 
discussion of the physiology of the group will be given later. 
The chief necessary conditions of life for Lawia zeylanica 
seem to be a rigid substratum on which to grow, preferably 
smooth rock, though it will grow on logs of wood or twigs 
fixed among the rocks ; (2) rapidly running water covering 
the plant ; (3) sufficient light. Like most of the other mem- 
bers of the order, it will not grow well, and in nature is very 
rarely found, in shady places on the rivers ; usually it occurs 
in spots which for part of the day at any rate are fully 
illuminated by the sun. 
The cultivation of this species is very difficult. I have 
succeeded in keeping it alive for some weeks in running 
E.g., on 28th April, 1898, I found such specimens 2-4 cm, long. 
(44) 
