CONTENTS OF SEEDS 253 



We never find some ripe seeds of a plant with 

 endosperm and some without, nor some plants of a 

 species with endospermous seeds others with exendos- 

 permous seeds. The different genera of a family are 

 also usually alike, though they sometimes differ in this 

 respect. It is important, therefore, in the determina- 

 tion of a plant to know whether the seeds are 

 endospermous or not. 



It must be remembered that, before the seed is 

 mature, there is nearly always some albumen to be 

 found, for that is always formed in the first instance. 

 Where seeds differ is in the disappearance of this 

 albumen on being consumed by the growing embryo, 

 or in its persistence as endosperm. 



There are differences, too, in the nature of the 

 endosperm. 



In the Castor-seed, it is oily oil is got from it by 

 pressure, and we have already learnt (p. 56) that 

 practically the whole seed consists of endosperm. 



In Paddy, Sorghum, Maize, Wheat, Ragi and other 

 grains the endosperm is mealy or farinaceous, i.e. can 

 be ground into a flour or meal. This is because it 

 consists mostly of dry starch. 



In the Date and other palms, it is very hard like 

 horn (horny), and in the Coconut it is both horny 

 and oily. In some species of MALVACEAE it swells up 

 and becomes slimy if wetted, and is said to be 

 mucilaginous or gummy, and in one variety of Maize 

 the American ' Sugar Corn ' it is sugary. 



There are often other substances in the endosperm 

 besides the main one ; thus the Castor-seed contains 

 nitrogenous substances, and a poisonous alkaloid (ricin) 



