23G 
WILIJS : PODOSTKMACEÆ 
Fruit small, sessile or stalked, smooth or 8- or 12-ribbed, isolobous or 
anisolobous, with oo seeds. 
Primary axis erect, non-floriferous in most cases, larger than in 
Podostemon. Thallus of phylogenetic root nature, closely attached 
to the rock by hairs at all points, exogenously branched or lobed, 
ribbon-like or crustaceous lichen-like. Secondary shoots acropetally 
formed, endogenous, at first in vegetative condition with included 
evanescent axis, later some or all floriferous, the axis emerging, 
apiscopic, and usually prostrate on the thallus, 1-flowered. Leaves in 
vegetative condition simple subulate, to 10 cm. long ; in floral buds 
some of them ultimately forming scaly bracts by the enlargement of 
sheathing bases and the fall of the leafy tips. Bracts 2-8, usually 
about 6, thicker on upper side. Spathe boat-shaped, enlarging at outer 
end, usually prostrate, and opening by a simple or compound slit 
on the upper side. 
India, Burma, and Ceylon, on water-worn rocks in rapids 
and waterfalls, common, polymorphic, 5 species. 
Endlicher’s original description of this genus is vague, 
and would include most of the Podostemeæ. He included 
in it the first two Indian species discovered, Dicræa Wallichii 
and Hydrobryum Griffithii. Tulasne redefined the genus 
to include H. Griffithii and the two species olivaceus and 
griseus of Gardner, which agree Avith it in having a boat- 
shaped spathe splitting along the upper side, and a ribbed 
capsule. He makes these into a sub-genus Zeylanidium 
characterized by simple stigmas, while H. Griffithii, with 
dentate stigmas, forms the sub-genus Euhydrohryum. 
Weddell, followed by Bentham, on a somewhat cursory 
examination of herbarium material, once more redefined 
the genus so as to include only the section Euhydrohryum ; 
his genus is thus based simply on the dentate stigmas and 
the 12-ribbed isolobous fruit. Now we have seen that the 
twelve ribs may at times occur in Dicræa ; the dentate stigma 
occurs in Hydrobryum lichenoides, Griffithella Hookeriana, 
and perhaps elsewhere, while at the same time examination 
of a large number of stigmas of Hydrobryum Griffithii shows 
that the stigmatic characters are extremely variable, every 
form from obcuneate to almost subulate occurring, as in H. 
lichenoides. The latter species and still more H. olivaceum 
