I.] STRUCTURE OF THE SEED 7 



water for a few hours, surround them with damp sawdust, 

 and then keep them in a warm place for a day or two in 

 order to start their germination. As soon, however, as 

 they have been well soaked they may be pulled to pieces, 

 and the function of each part can be followed up day 

 by day as the growth advances. Taking first the bean, 

 we begin by finding a tough outer skin, which after 

 soaking can be peeled off entirely ; when the plant 

 germinates under natural conditions, this skin is burst 

 and thrown off. Under the skin we find the mass of the 

 seed, which splits at once into two flat discs, united at 

 one point by a small structure, that for the moment we 

 may liken to a hinge. Notice the position of this hinge 

 with regard to the markings in the seed coat which 

 indicate where the bean was attached to the pod, and 

 therefore to the parent plant. The meaning of the 

 structure of the bean will only become plain by following 

 up the successive stages in its growth. It will then be 

 seen that what we have called the hinge develops into 

 the future plant ; it puts out a root, and in the opposite 

 direction it elongates into a shoot, from the tip of 

 which leaves begin to unfold — it is indeed the " embryo," 

 the seat of life in the plant. The two flat discs which 

 are united by the embryo open apart and set them- 

 selves at right angles to the new stem, if the plant is 

 being grown in the ordinary way ; in the open air they 

 become green, but at the same time they slowly shrink 

 and become emptied of their contents, finally they 

 shrivel and drop off. They are known as " cotyledons," 

 or seed leaves. In the case of the maize the structure 

 is somewhat different ; at one end of the grain will be 

 found, as before, the embryo from which proceed the 

 rootlets, no longer a single one but several, and a shoot 

 which shows a single leaf. The greater part of the grain, 

 however, is occupied not by a pair of seed leaves, but 



