Natural History 635 



are set up. There comes a point, usually when the sun is hot, 

 when the junction of the valves gives way, and, with a little 

 report, they flick into spirals, jerking the seeds out to a distance 

 of some feet. It is not far, but it is far enough to prevent that 

 immediate overcrowding which would occur if all the harvest 

 of the bush fell straight to earth. Then the seeds may be carried 

 away by ants for the sake of their little orange oil bodies; these 

 travel further, and if they come to be buried, not too deep, in an 

 anthill, their chance of germinating in favourable conditions is 

 rather increased. 



Many plants depend on animals for seed distribution. The 

 burr of the goose-grass is a dry fruit covered with hooked spines, 

 which catch in the coat of a passing sheep or rabbit. The water- 

 fowl lifts a little dab of mud as it rises and flies to a fresh marsh. 

 In the mud there may be a dozen seeds. But most conspicuously 

 adapted for animal distribution are the fleshy fruits, attracting 

 by their colour and rewarding by their food-value. The seeds of 

 such fruits apple, cherry, gooseberry are protected by very 

 resistant coats, and pass undigested through the animal's food- 

 canal. The germinating seedling benefits from the circumstances 

 of its deposition. The thrush eats the berries of the mistletoe, 

 and wipes the seeds off its bill on to the bough on which it sits. 

 The seeds adhere firmly to the branch as the glutinous juice 

 dries, and in the following spring germinate in the position they 

 require. 



Movements of wind and water carry seeds to great distances. 

 Darwin showed that many seeds can float on salt water for weeks 

 or even months and germinate at the end. By ocean currents 

 the vegetation of strand and mangrove swamp has spread through 

 great regions of the Tropics. It is probable, too, that seeds of 

 inland plants washed down rivers, stuck in crevices of sticks, have 

 crossed the seas and colonised new countries. 



The wing of the maple fruit, of the pine seed, of the ash, 

 allows the burden it supports to volplane through long distances 



