OF CEYLON AND INDIA. 
429 
find in the N^^mphæaceæ or other orders of water plants. 
It opens only in comparatively dry air, and the seeds ai*e 
adapted to land existence for some time before germina- 
tion. They ultimately germinate under water, but they are 
not suited to being shed in the first place into water. If 
dropped into water from the capsule they are carried away 
down stream, and have almost no chance or prospect of 
becoming attached in a place suitable for growth. One is 
surprised on the whole, in dealing with this order, to find 
so little provision for germination of the seeds in suitable 
places, where they can live and fiourish. The only advan- 
tageous quality they seem to have in this respect is their 
small size, which helps them to cling in crevices of the rock 
or of the old thallus, but we must probably regard this as 
derived from their land ancestors, not as an adaptation. 
The mucilaginous outer coat, again, is rather a character of 
a land plant, and probably survives in the Podostemaceæ 
without being of any particular value to them in connec- 
tion with their mode of life, though indirectly it must be of 
service. Wading birds may often be seen walking with 
wet feet over the fruiting thalli, and probably sometimes 
carry seeds to other localities. When a seed falls into a crack 
in an old thallus the swelling and subsequent shrinkage 
perhaps help to drive it well in. The fruit is very uniform 
throughout the order, the bicarpelled many-seeded symmetri- 
cal form persisting from Weddellina down to many of the 
Eupodostemeæ, e.g.^ Dicræa. Here at last, however, the 
progressive dorsiventrality of the plants seems to show also 
in the fruit, and in Podostemon and Griffithella, Willisia, 
Hydrobryum, and Farmeria, the fruit is structurally dor- 
siventral, with unequal lobes. As Dicræa and Podostemon 
and Hydrobryum all live in similar circumstances, and all 
simply shed their seeds upon the rock as soon as the erect 
fruit opens, we cannot regard the asymmetrical develop- 
ment of the fruit as of any direct advantage ; it would 
appear rather to be an expression of the continually increas- 
ing dorsiventrality of the floral parts in correlation with 
