SEEDS AND FRUITS. I4I 
similar state of matters exists in some sz/iquas, where the valves 
suddenly fly up from below on the slightest touch. A good 
example of this is a small cruciferous! plant with white flowers, 
the hairy bittercress (Cardamine hirsuta), which grows abundantly 
in waste places. A hand passed lghtly over a patch of these 
plants, when the fruits are ripe, elicits a brisk discharge of 
seeds. 
Capsules are adapted in some cases for throwing their seeds to 
a distance, of which the dog-violet is a very good example. Here 
the capsule bears three rows of seeds on parietal placentas, When 
ripe, it splits between these into three valves, which separate widely. 
The edges of each valve now curl up and press against the seeds, 
here extremely smooth, with the result that they are shot to some 
distance, just as an orange pip can be projected from between the 
finger and thumb. 
Succulent fruits are but rarely adapted for ejecting their seeds, 
but this is the case with the squirting cucumber, common in South 
Europe. ‘The ripe fruit is in such a state of tension that the 
lightest touch separates it from the stalk and causes the contents 
to squirt out with much force. 
(2.) Water effects the distribution of many seeds, especially 
such as are enclosed in a covering which is watertight and at 
the same time light enough to make them float. Experiments 
have been made on this head, leading to the conclusion that the 
seeds of about one plant in ten could be floated across a sea goo 
miles broad and still remain capable of germination. Earth, 
containing seeds, may also be carried for long distances in the 
crevices of drift-timber. The cocoa-nut is one of the best examples 
of a fruit which is safely transported by water for an immense 
distance without injury. Owing to this it is common on the 
coral islands of the Pacific. . 
(3.) Wind plays a very important part in the dispersal of 
seeds. ‘These are sometimes suited for this by their small size, 
as in orchids. Such small seeds are often found in porous 
capsules, like those of snapdragon and poppy, and in these the 
pores are situated near the top. The seeds cannot, therefore, 
fall out, but are shaken out by the wind. Each pore in the 
poppy capsule is provided with a little flap on the lower side, 
which is said to move up and close the pore in damp weather. 
Coverings or tufts of hair are often present upon seeds and 
fruits, materially assisting in their dispersal by wind. The 
commonest example is found in the “ pappus ” of many Composites, 
a sort of crown, representing the calyx, which surmounts the 
1 With cross-shaped corolla (¢f. Appendix A), a characteristic of the group 
Crucifere, of which wallflower and stuck are typical examples. 
