8 JVHAT THE PLANT IS MADE OF [chap. 



by a mass of material which remains attached to the 

 side of the stem of the young plant. As the plant 

 grows the seed material gradually disappears, until after 

 a time only an empty husk remains, and then falls off. 

 In the case of maize and similar seeds like wheat and 

 barley, which begin by throwing up only a single leaf, 

 this attached food store does the work of the seed 

 leaves in the bean and similar plants, and is known as 

 the endosperm. Now take some of the soaked seeds 

 and mutilate them in various ways before setting them 

 to germinate : cut out the embryo, cut bits off the 

 embryo, poison it by touching it with a trace of carbolic 

 acid or a drop of boiling water, cut off one cotyledon or 

 half of both cotyledons, cut off a large and a small part 

 of the endosperm. 



The seeds will not grow at all if the embryo is cut 

 out and killed or much mutilated, but the embryo itself 

 will make a start to grow without cotyledons or endo- 

 sperm, though the length of time it will subsist will 

 depend on how much of the latter has been left to it. 

 The embryo is in fact the seat of life in the seed, 

 the rest (cotyledons or endosperm) is dead food material 

 stored up by the parent plant to give sustenance to the 

 new plant (embryo) until it can establish itself in the 

 world. It has been found possible to grow an embryo 

 removed from its endosperm on blotting paper or 

 similar porous material, if it is kept moistened with an 

 appropriate food solution containing sugars, <^-proteins, 

 and similar plant constituents. 



We may now sum up the facts we have ascertained 

 about the seed : it possesses a coat of one or more 

 membranes, an embryo (which is the seat of the life of 

 the seed), and a food store for the nutrition of the embryo 

 until it has sufificiently developed to feed itself on the 

 soil and the air, and this food store may take the form 



