136 BRITISH PLANTS 



reject the seeds. This serves the plant very well, for the 

 result is the distribution of the seed. 



(a) Fruits. Before the seeds are ready for dispersal, the 

 ripening fruits must be protected against weather, against 

 disease, and against the chances of being prematurely 

 eaten and destroyed. This is secured in various ways. 

 Many succulent fruits contain antiseptic oils, aromatic or 

 bitter principles, or similar substances equally unpleasant 

 to animals searching for food, and germs that might 

 destroy. Unripe fruits are hard, sour, unattractive, and 

 unpalatable. Some have a bitter rind like the orange, 

 others are covered by a coating of wax, others are fur- 

 nished with disagreeable hairs, and others are defended 

 by an armour of spines. 



Among succulent fruits we have the stone-fruit, or drupe 

 e.g., peach and the soft-fruit, or berry e.g., grape. 

 In the drupe the fleshy part is eaten by birds, and the 

 stone containing the seed is rejected. To keep the fruit 

 from drying up before the seeds are ripe, as well as 

 to keep off external water, the outside is protected by 

 a dense elastic skin, frequently covered over with wax or 

 " bloom " e.g., plum. This wax is antiseptic, and pre- 

 serves the fruit against the attack of fungi and bacteria, 

 which would cause it to go rotten before it is ripe enough 

 to attract the birds. It is important, therefore, that the 

 continuity of the skin should be kept intact, since wounds 

 and abrasions lay bare the deeper unprotected tissues, and 

 expose them to disease. In the berry the whole fruit is 

 fleshy, but the seeds are hard and indigestible. Even if they 

 are swallowed by birds, the seeds pass uninjured through 

 their bodies. Some berries e.g., deadly nightshade are 

 poisonous, and can only be eaten with impunity by a few 

 birds which have become constitutionally used to them. 



Nuts have either tough leathery shells or hard stony 

 cases. These prevent the seeds from being eaten except 

 by those animals whose teeth are strong enough to open 

 the shells, and which alone are capable of effectively dis- 

 tributing the contents. At the same time some means 

 are always adopted to protect the nuts while they are 

 young and tender. In some cases the sepals enlarge and 

 envelop them. In the acorn and hazel, bracts coalesce and 

 form cupules (Fig. 47) ; in the beech and chestnut they 

 form spiny shells (Fig. 48). 



