156 FIELD, FOREST AND FARM 



perisperm. The almond, acorn, pea, bean, with a 

 host of others, are quite lacking in anything of the 

 sort, having under the skin only the germ and noth- 

 ing more, absolutely nothing. The reason for this 

 difference is plain enough. The almond, bean, pea, 

 acorn, with their big cotyledons bursting with nu- 

 tritive matter, do not need a supplementary ration; 

 the germ will be sufficiently suckled by the udders 

 nature has provided in the form of these cotyledons. 

 But the ivy, with its poor little cotyledons, calls for 

 help, and finds it in the farinaceous storehouse of 

 the perisperm. 



"Thus a seed may have a double supply of nour- 

 ishment to meet the needs of the young plant : that 

 contained in the cotyledons and that stored up in 

 the perisperm. Cotyledons are never lacking, but 

 the perisperm is not found in all seeds. There is 

 none in the almond, acorn, chestnut, apricot, bean, or 

 pea; but to make up for this lack their cotyledons 

 are of considerable size. On the other hand, buck- 

 wheat, chickweed, and ivy, whose cotyledons are 

 small, are provided with a perisperm. All this may 

 be reduced to one general rule. Cotyledons and 

 perisperm play similar parts: they both help to 

 nourish the little plant in its infancy. So, generally 

 speaking, the seed with large cotyledons has no per- 

 isperm, while the seed with small cotyledons has one. 



"I have just told you that many plants have only 

 one cotyledon. I will add that this cotyledon is usu- 

 ally very small. It is especially in these plants that 

 the perisperm is present. The grain of wheat offers 



