OF CEYLON AND INDIA. ' 
281 
many are completely dry, and in none is there more than a 
mere trickle of water. In this the few Podostemaceæ that 
have not yet fruited are found, their green or red thalli 
shining brightly in the sun and forming a very pretty sight. 
On the rocks above the water-level are thousands of fruits 
borne on the dead withered thalli. Higher still, and this is 
a circumstance of rare occurrence with the greater uni- 
formity of level of the Ceylon rivers, may be seen dry plants, 
which have been exposed so early in the season that they 
have not formed any flowers, and at times even seedlings 
may be found by any one who has seen them in the living 
condition, and thus can recognize them. A good deal of 
information was obtained from the study of the early stages 
thus preserved. The rejuvenescence of the thallus, on the 
other hand, which is so marked a feature of the Ceylon 
forms, enabling them to overcome the difficulties caused by 
changes in the water-level between the rainy seasons, is rarer 
and of less importance in the Bombay districts, where the 
rivers run quite dry. 
At Darjiling the periodicity must evidently be very much 
the same as in the Merkara district of the Western Ghats, 
Only one species has been recorded from Sikkim, Hydro- 
bryum Griflithii, found by the Rev. P. Decoly in a stream 
near Kurseong. I visited this stream, and found it to be one 
of the rivers of the foot-hills, rising at about 7,000 feet, and 
thus not fed in summer by snowwater. No Podostemaceæ 
have as yet been found in streams fed by melting snows. 
In the Khasia hills of Assam the periodicity is very 
similar. I spent part of December, 1901, among these hills. 
The season had been fairly normal as regards rainfall, but 
the water in the rivers was far less low than in the Bombay 
Ghats, though low enough to have exposed most of the 
Podostemaceæ. In general the rivers were like those of 
Ceylon in this respect, and they evidently do not run dry 
like the Bombay streams. Many of the plants showed a 
certain amount of rejuvenescence where they were still 
covered with water. Hooker, in his Himalayan Journals 
