FOOD MATERIALS IN SEEDS 65 



Then the cotyledon or cotyledons swell and, if there 

 is endosperm, absorb it, dissolving it with a special 

 digestive substance secreted by them. 



What follows after this depends on the nature of 

 the plant. In some, as the Broad-bean, Pea and Maize, 

 the cotyledon remains in the seed, and is said to be 

 hypogeal. In others, Palms and Onions, it comes partly 

 out and pushes the radicle further into the earth ; in 

 others again it is drawn up out of the seed by the arched 

 hypocotyl and brought up above the ground, and then 

 it is said to be epigeal. If there is endosperm the coty- 

 ledons are thin, but if there is not, they are nearly 

 always rather thick because they contain food mate- 

 rial and then as the young plant grows become 

 thin and wasted. In every case the young plant begins 

 its life on the food stored in the seed by the mother 

 plant. This stored food consists always of large quan- 

 tities of carbonaceous matter and some nitrogenous and 

 proteid substances. The carbonaceous matter differs 

 in different plants ; in some it is a carbohydrate 

 starch and seeds with starchy endosperms or coty- 

 ledons form valuable articles of food, such as all cereal 

 grains and pulses. In others it is a different kind of 

 carbohydrate, cellulose, as in the Date and Palms 

 generally, and is useless as a food for man, but can be 

 eaten by many animals. In others again it is oily in 

 nature, as Castor, Sunflower, Cotton. In a few it is 

 sugar, as in the Sugar-corn, a special variety of Maize. 



12. All these substances are highly concentrated 



food-stuffs, packed in the seed by the mother-plant for 



the benefit of the next generation. And if we consider 



the hundreds of thousands of seeds that most plants 



5 



