352 WILLIS: MORPHOLOGY OP THE PODOSTEMACEÆ 
striata, the Banna form, I have only seen herbarium material, 
and probably enough when good material is available it 
may prove specifically distinct. The following remarks 
refer only to the Khasia mountain form, D. Wallichii 
Khasiana, which I have myself studied at Cherrapunji, the 
district in which the plant was originally collected. I have 
also examined the herbarium material. 
Habitat. —'Vh.Q plant grows in very similar situations to 
D. elongata, on rocky substratum in rapidly flowing water. 
Owing to the enormous rainfall of Cherrapunji, there must 
be considerable depth and force of water during the vege- 
tative season, I found it in one or two places growing 
slightly intermingled with Hydrobryum lichenoides. 
Dry Season Appearance . — A number of specimens are 
figured in PL XXL As usually seen at Cherra, the plant 
consists at this time of brown thalli, a few millimetres wide 
and almost as thick, attached at the base by a sort of foot, 
and running outwards from it, usually down stream, in a 
branched laciniate form, to perhaps 5-10 cm. long. On the 
ends of the laciniate arms the fruits are borne, usually one 
on each, on a stalk of about 8 mm. long. 
Mature Structure . — The most of the dried material in the 
herbaria gives little clue to the mature structure of the living 
plant, which is really very like that of D. stylosa, com- 
paratively little branched, and with broad lobes, not with 
laciniæ. In most essential points the structure is that of the 
latter species, to wiiich reference may be made for details. 
The thallus is usually attached at the base only, or at the 
base and a few outer points, only rarely at all points. At 
the base, where the primary axis formerly stood, there is a 
sort of stout cup-shaped foot, seen from below in PL XX., 
fig. 14. From this the thallus spreads out, chiefly in one 
direction, that of the prevailing current, so far as I have been 
able to observe. In general it has the habit and construction 
of a Fucus, with broad crisp undulated lobes just as 
described below for D. stylosa, var. fucoides. Plate XXI. 
shows a series of specimens from above and below the water. 
