378 WTLLTS : MORPHOLOGY OF THE PODOSTEMACEÆ 
Later on, as the flowering season approaches, the develop- 
ment of the flowei s takes place, most of the secondary shoots 
producing each a single terminal flower. The axis elongates 
and becomes prostrate on the thallus(or nearly erect in some 
varieties), pointing in all cases towards the tip. The bracts, 
2-8 in number, which form on each shoot, are developed 
just like those of Dicræa, by the enlargement of the sheathing 
bases of the leaves and the fall of the tips. The upper 
exposed side of the sheath is thick and siliceous, the lower 
thin and membranous. At the end of the shoot is the flower 
enclosed in the usually prostrate spathe (PI. XXXIL, fig. 3). 
When exposed to the air by the fall of the water (and thus, 
owing to the very dwarf habit, almost only at a time when 
the water is about to leave the plant altogether), the spathe 
splits in a more or less irregular way on the upper side, and 
the flower emerges on a short stalk and stands erect. Like 
all the other flowers we have described, it seems anemophi- 
lous and self-fertilized, with the chance of a cross at times 
owing to the nearness of the flowers to one another on the 
rock. 
The structure of the flower has already been sufficiently 
described. The chief point of importance to be noted here, 
as bearing on the taxonomy, is the great variability to be 
found among the stigmas, of which a few instances are figured 
in PI. XXXIL, figs. 5, 6 (and cf. PL XXXVL, fig. 8). The 
average form perhaps is ovate, but every stage may be found 
from simple narrow subulate to broadly obcuneate with 
many teeth. As the latter form of stigma is the character 
on which Weddell chiefly bases his reduction of the genus 
Hydrobryum to the solitary species H. Griffithii, and we 
shall find the same variability in the stigmas of this species 
also, it is evident that this character is not generic. 
The fruit soon ripens, andis anisolobous with one deciduous 
valve. It has eight ribs, well marked in most cases, but 
almost evanescent in some of the varieties. In some, too, the 
ribs are confluent some distance below the tip of the fruit, 
in others only at the tip. 
