376 WILLIS : MORPHOLOGY OP THE PODOSTEMACEÆ 
purposes of the present paper, however, this variation does 
not matter much, being chiefly in features that need only be 
briefly touched upon, 
Hahitat . — The plant affects smooth rocks in rapid currents, 
but on the whole is not found in quite such violent water as 
H. olivaceum. It occurs very commonly in quite small 
streams, where the risk of shallow water is great, just as do 
the other Hydrobryums and Lawia zeylanica, and perhaps 
correlated with this is the fact that it occurs at much higher 
€ilevations than most of the Indian Podostemaceæ. In Ceylon 
it is rare, occurring only, so far as yet known, in one river, 
at a height of 3,500-4,000 feet. In this river there is not, so 
far as yet known, any other species of the family. In the 
Sholai-aar, in the Anamalai mountains, it is commoner, 
and is mixed with H. olivaceum, and also, as PI. XXVIII. 
shows, with Willisia selaginoides. Mr. Barber found it in 
Kanara, and I myself found it in enormous quantities every- 
where in 1 he Khandala district, where it is most conspicuous, 
and accompanies Lawia zeylanica in almost every stream. 
It is difficult to understand how it has been overlooked in 
this district, but in the Museum at Kew I found some 
specimens from the Bombay Ghats collected by^ Law, and 
labelled as Lawia pulchella. It is also frequent in the 
Cherrapunji district at 4,500 feet, and often mixed with 
Dicræa Wallichii, and I found it at Shillong and in the 
foothills between Shillong and Gauhati. 
Dry Seaso 7 i Apiwarance . — This is well shown in exposed 
plants in PI. XXXI., and in plants from just below the 
water-level in PI. XXYIII. Most of the plants in the first- 
mentioned plate are from the Khandala district, where this 
plant is to be seen in its greatest luxuriance and development. 
The rock is covered with creeping thalli, as closely and firmly 
attached as those of Lawia, a few millimetres broad, and 
tapering towards the tip, brown, gray, blackish, or nearly 
white, acccording to the form and the locality. They are 
very regularly branched, alternately or sub-oppositely, with 
little prosti'ate shoots in the forks of the thalli, from each of 
