Elementary Botany 



the skin from off the seed, leaving a whitish fleshy mass within. 

 This skin is really, however, double, as can easily be proved 

 by peeling from the interior a thin pellicle. 



These coats are collectively known as spermoderm ; the 

 outer being called the testa, and the inner the tegmen. 



The mass within the spermoderm forms the nucleus of the 

 seed. In the case of the Broad Bean this nucleus is entirely 

 made up of the young plant or embryo. At one end there is 

 a pointed portion which is directed towards the micropyle. 

 This is destined on germination to be prolonged to form the 

 root, and is known as the radicle (fig. i). 



Fig. 2. — Longitudinal section 

 of a seed of Oat : a, endo- 

 sperm ; c, the single cotyle- 

 don : G, plumule : R, radi- 

 cle ; T, testa ; o, hairs. 



Fig. 3.— Germination of the 

 Oat : a, cotyledon ; ff, axis 

 of the embryo ; rt', radicle ; 

 f^ plumule. 



The great mass of the nucleus is made up of two fleshy 

 lobes, which can easily be separated from one another— the 

 cotyledons ; and between these at the top of the radicle there 

 IS a little portion curved over and divided at the end in a plume- 

 like manner. This, which is known as the plumule, will, under 

 favourable circumstances, grow into the stem and leaves of the 

 future plant. 



In some seeds, as, for instance, those of the varieties of corn 

 and grass, there is in the nucleus a substance, albumen, in 

 addition to the embryo of the plant (fig. 2). This albumen 



