DISPERSAL OF SEEDS 



97 



the wind, or by clinging to animals, the fruits are dry, whereas 

 seeds or fruits which are dispersed by being carried inside 

 animals are usually possessed of conspicuous and fleshy coats, 

 which invite animals to notice and eat them. The fruits 

 being eaten, the seeds are protected by an indigestible stone 

 (in drupes) or testa (in berries and Gymnospermous fruits), and 

 pass through the body of the animal uninjured. When the 

 fruit is indehiscent it is usually the pericarp which is succulent 

 and invites the animals which effect the dispersal of the fruit. 

 When, on the other hand, the carpels are, open, as in Gym- 

 nosperms and dehiscent fruits, the seed is often brightly 

 coloured, and may have a . succulent inviting outgrowth (the 

 aril). 



Protection of the embryo in the seed. — The embryo and 

 food-substance inside the testa require protection against 

 climatic influences which would hasten their disorganisation 

 and decay, and against attacks on the part of animals and 

 fungi. The embryo and food-substance are therefore protected 

 by a firm hard coat. When the fruit is dehiscent and the seeds 

 travel naked, the testa is thick and strong (f.g. Wallflower, 

 Bean). When the fruit is dry, indehiscent or separating, the 

 seed is protected by the pericarp, and there is no necessity for 

 the testa to be so thick — in fact, it may be quite imperceptible 

 or absent (e.g. Grasses). Finally, in fleshy indehiscent fruits 

 the stony layer of the pericarp of drupes protects the embryo, 

 and the testa is thin, whereas in berries there is no stony 

 layer, so that the testa of the seed must be well developed 



