OF CEYLON AND INDIA. 
327 
P0D08TEM0N. 
[Michx. ; Willis, Rev. Podost. Ind., Ann. Perad., I., p. 228.] 
As already explained in the preceding paper, the Indian 
flora contains no representatives of the systematic groups 
which intervene between the Tristicheæ and the Eupodoste- 
meæ, with the latter of which we have now to deal for the 
rest of this paper. In the systematic order there followed 
Podostemon comes after Dicræa, but for morphological 
purposes it is perhaps simpler to take the former first, as in 
it the secondary shoots are still of considerable size, and take 
the chief part in assimilation, whereas in Dicræa and nearly 
all the following genera they are very much reduced as 
compared with the thallus. 
As elsewhere explained, I have excluded from the genus 
most of the species placed in it by Bentham, who is followed 
by Hooker in his Flora of British India ; these species are 
considered under Dicræa, Hydrobryum, Griffithella, and 
Willisia. There can be little doubt that Bentham’s fusion of 
all these went either too far or not far enough, for if these 
be united with Podostemon there is no valid reason for 
keeping either Mniopsis, Oserya, Devillea, or Ceratolacis 
separate from it, whereas in the Indian species which he did 
unite with Podostemon there is very great morphological 
variety, as we shall see. 
The genus, as now defined, is confined to America and 
India, so far as our present knowledge goes, and includes in 
India and Ceylon two very isolated forms, P. subulatus, 
Gardn.,and P. Barberi, Willis, to which perhaps should also 
be added Polypleurum Schmidtianum, Warming, lately 
discovered in Siam. 
Our knowledge of the morphology of this genus is com- 
paratively good and complete, thanks to the labours of Prof. 
Warming, who has described the thallus, secondary shoots, 
and flowers, in many different species from America, and in 
P. subulatus from Ceylon material collected by Trimen. The 
American species mostly show a creeping thread-like thallus 
