SEED. GERMINATION 9 



When the shoot of the Bean has grown to the length of about 

 six inches, it will be seen to consist of a central Stem terminated by 

 a bud. Leaves, of which the lowest are pale-coloured scales, are 

 bome laterally on the stem. Passing upwards from the base succes- 

 sively larger leaves are met, each with broad green lobes and a sheath- 

 ing base. Passing on from these mature leaves, we come to the bud. 

 Dissection of the bud shows that it is composed of a series of succes- 

 sively more minute leaves, very delicate in texture, closely overlapping 

 one another, and all seated on the shortened axis. A bud is thus a 

 compact young shoot, consisting of a short stem overlapped by crowded, 

 immature leaves. 



As the shoot develops, a new bud appears in the axil, or angle 

 of insertion of each leaf upon the stem. Even the cotyledons of the 

 Bean may bear such axillary buds. They are constructed like the 

 apical bud, and on development each may repeat the characters of 

 the main shoot. Provision is thus made for multiplication of shoots 

 so as to form a branched shoot-system. 



The Bean-Seed itself has throughout germination remained below 

 ground. Its fleshy seed-leaves do not emerge from the seed-coat, 

 but are there gradually emptied of their nutritive store, and finally 

 rot away. Their sole function is storage of food-material for the 

 germ. But in other plants the behaviour is different. A good example 

 is seen in the Charlock. Its seed is nearly spherical, with slightly 

 flattened sides. A lateral scar of attachment (hilum) is seen, as in 

 the Bean, and the seed is covered by a tough leathery seed-coat. 

 Within this is the embryo, with two cotyledons, a bud or plumule, and 

 a first root or radicle. But here the cotyledons are folded sharply in 

 a median plane, giving a compactness to the embryo, which fills the 

 spherical seed (Fig. 3, i. ii-). On germination the seed-coat is burst by 

 the enlarging germ, and the root emerges as before, curving at once 

 downwards (iii.). But here the part of the stem or axis below the 

 seed-leaves grows quickly in length. At first it shows a strong 

 arching curve (iv.). But later this is straightened out, with the 

 consequence that the cotyledons and the bud are carried above 

 ground, still covered by the protecting coat. It soon falls away, 

 and the cotyledons expand, diverging as green leaves, with the bud 

 between them (vi. vii.). The latter elongates as it grows older, 

 forming the leafy shoot. Thus the parts of the seedling of the 

 Charlock are numerically and relatively as in the Bean, and in both 

 cases the food-supply is in the fleshy cotyledons. The difference 

 lies in the fact that in the Bean the active growth is in the region of 



