62 THE LIFE OF THE PLANT 



In an hour, or even less, a small snow-white rootlet 

 protrudes from a slit in the testa ; sometimes the entire 

 little embryo is pushed out afterwards. What happens 

 is this : the endosperm of the coffee bean, although 

 as hard as horn, becomes soft and very elastic through 

 the action of the boiling water or of the alkali, and in 

 swelling compresses the embryo and squeezes it from 

 its place. 



We see therefore that seeds may be of two kinds : 

 in some we find very well developed fleshy cotyledons ; 

 in others mealy, oily, or hard and horny endosperm. 

 Just as cotyledons shrink and decrease in size during 

 germination, so also the endosperm disappears little 

 by little, being apparently absorbed. This arouses the 

 suspicion as to whether the decrease of substance in the 

 cotyledon or endosperm is not connected in some way 

 with the increase in size of the shoot, i.e. whether the 

 development of the young plant is not achieved at the 

 expense of the food-substances stored up in the cotyledon 

 or endosperm. But all these substances are also 

 present in a resting seed ; why then is their displacement 

 manifested only during germination ? The answer to 

 this question will be apparent if we recall what we 

 learnt in our last lecture. The nutrient substances in 

 the endosperm or cotyledons exist in a solid and, 

 generally speaking, insoluble form. You remember 

 our analysis of flour, i.e. of powdered seeds. We 

 detected there insoluble starch, insoluble gluten, and 

 oil. All these substances are immobile and incapable 

 of diffusion from one cell to another, a property which 

 is quite essential to them as reserve foods, since other- 

 wise they would not remain stored up. 



Hence we have in the seed an embryo, and in a certain 

 part of the embryo the cotyledons ; or in its immediate 

 neighbourhood, in the endosperm, we have stores of 

 nutrient substances in an immobile form, and on that 

 account inaccessible to the embryo. We now inquire 



