THE DISPERSION' OF SEEDS AND SPORES. 61 



The chances are now that the upper extremity of 

 the awn has been applied to a new point of resistance, 

 so that the next rain will send the seed still deeper 

 into the soil, and so with every succeeding change 

 of weather. Erodium glaucoxyhylluin has the upper 

 part of its awn feathered, the more certainly to 

 secure that it will press against some resisting 

 object when it begins to unwind itself. In the 

 common E. cicutariiini the awn is not feathered. 

 In this genus the seeds may literally be said to screw 

 themselves into the earth ; and the same applies to 

 Anemone tnontana, which has an awned achene 

 capable of bui-ying itself in this manner. The 

 feather-grass {Stipa pennata) has the same peculiarity, 

 and perhaps also some species of Clematis. Avena 

 sterilis has a hygroscopic awn, by means of which 

 the seed can shift from place to place. Possibly it 

 may also be of use in enabling the seed to penetrate 

 the soil. Aristate grains and seeds fall, however, to 

 be considered in another connection. Here we may 

 recall the fact that many plants bury their seed- 

 pods in the soil, e.g.: Linaria Cymbalaria, Trifolium, 

 suhterraneum, Arachis hypogea, Cardamine chenopodi- 

 folia, etc. This, however, is more likely to be due 

 to an aversion towards light (aheliotropism), or to 

 the action of gravity (geotropism), than to hygrosco- 

 pic action. 



To the class of schizocarps also belongs the 

 remarkable fruit of Hura crepitans, called the 

 "monkey's dinner-bell" because its woody carpels 

 when quite dry separate suddenly with a noise like 

 the report of a musket. The stellate capsule of the 

 ice-plant {Mesembryanthemwm) is very hygrometric, 

 and opens when moistened. 



Oxalis has a seed with an elastic testa, by the 

 sudden rupture of which the central core of the 

 seed is projected out to a considerable distance. The 

 hairy -cress {Cardamine hirsuta) is a well-known 

 example of an elastic fruit. If the ripe siliqua be 

 touched, its two valves quickly curl up and the seeds 



