218 
WILLIS : PODOSTEMACBÆ 
of the forms, and the grouping of the Dicræas under Podos- 
temon, as in Bentham and Hooker’s Genera Plantarum and 
in the Flora of British India, is still more artificial, com- 
pletely breaking up the genus and including in the section 
Dicræa the markedly different form Podostemon subulatus. 
Weddell spoiled the genus by admitting the smooth 
anisolobous-fruited Willisia selaginoides. 
The Dicræas are very abundant in all the Podostemaceæ 
regions of India and Ceylon, and are extraordinarily variable 
and polymorphic. It is not yet possible to draw good specific 
limits, and unsafe to try to define varietal forms. I give 
below a tentative grouping of the forms studied by myself 
in fresh and preserved material, and have drawn the specific 
limits very widely. 
Owing to the curious way in which the parts of thethallus 
not directly concerned in the production and nutrition of the 
flowers and fruit break away towards the end of the life of 
the plant, there is a great difference in the morphological 
structure, as already mentioned (p. 191), between the sub- 
merged plants and the dry fruiting specimens, in most cases. 
This will be more clear after the appearance of the figures 
illustrating the genus in the subsequent paper. 
We have so little knowledge of the Madagascar species that 
it may easily prove to be the case that they are generically 
distinct, in which case our genus will have to be re-named. 
Madagascar, Ceylon, Travancore, and Anamalai Mountains 
to Kanara, Khasia Mountains of Assam, Burma. Abundant 
in all districts mentioned, variable. 
Dicrœœ indicœ. 
Thallus narrow, long, with creeping basal portion and 
free distal. Secondary shoots (floral buds) sessile on thallus 
by narrow base and tapering downwards, or stalked, often 
linear or narrow oblong. 
Thallus cylindrical, filamentous, to 50 
cm. long in free parts ; pedicel of 
fruit about 8 mm. ...D. elongata, Tul. 
