592 



BOTANY OF THE LIVING PLANT 



Some plants show curvatures of the fruit-stalk, or of the shoot 

 generally, which aid in the dissemination, or even in the exact deposit 

 of the seeds. The fruit-stalk of the Ivy-leaved Toad-Flax directs 

 its fruit to the crannies of the rock or wall in which it grows, so that 

 its seeds are shed directly on the spot suitable for their germination. 

 Some denizens of arid soil curl up their branches as they dry into a 

 sphere, which when detached may be rolled great distances by the 

 wind over flat ground, scattering their seeds as they go. This is 

 seen in the " Rose of Jericho '^ and in the Grass, Spinifex. It is 

 shown graphically in a species of Salsola which grows on the coast 

 near Adelaide (Fig. 237). 



Dissemination by Animals. 



In various ways Plants may make use of the free movements of 

 animals^ which while serving their own ends become the involuntary 

 agents of dispersal. The living seeds may be conveyed by them 



Fig. 238. 

 Fruits with hooked outgrowths, effective in transfer by animals. .-1 = Agrimonia 

 (LeMaout). /? = Grt//»;;r (Lo Maout). r-=Cynoglossum. D = Geum. £ = Bidcns. 



externally^ attached to their coats or other parts of their bodies : 

 or internally, as ingested food : or they may be actually carried by 

 them intentionally. For the first no special development is actually 

 necessary in the seed or fruit. They may stick to the feet of animals 

 clogged with mud, especially birds. Darwin removed the soil from 

 the foot of an injured partridge, and obtained from it no less than 

 82 seedlings. But many fruits and seeds are provided with means 

 of attachment ; where the seeds are small, a sticky glandular secretion 

 may serve, as in some Salvias. But many fruits develop as " burs," 

 being provided with hooks of various origin, which attach them 

 to fur or feathers. In the Burdock the tips of the bracts are hooked : 

 in Bidens spines representing the calyx bear reflexed teeth (Fig. 

 238, 'E) : in Cleavers (5), or the Carrot there are hooked emergences 

 on the wall of the inferior ovarv : in the " Echinella " section of the 



