GERMINATION OF SEEDS 



85 



only such features as have an evident bearing upon its 

 germination will be considered here. The seed is invested 

 by a hard coat (testa), which in some seeds is extremely 

 hard, and is evidently a protective structure during the 

 more or less prolonged period of 

 rest. Within the testa the young 

 plantlet is packed, at this stage 

 called the embryo (Fig. 81). The 

 process of germination is the 

 escape of this plantlet from the 

 testa. If the embryo of the bean 

 be removed from the testa better 



FIG. 81a. Section of violet seed, showing 

 embryo, endosperm, and testa. 



FIG. 82. Seedling of bean: 

 A, embryo removed from 

 testa; B, young seedling 

 showing hypocotyl, cotyle- 

 dons, and plumule; C, older 

 seedling showing the first 

 internode and leaves of the 

 stem. After GRAY. 



done after soaking in water for 



some time and straightened out, 



it will be found to consist of three 



distinct parts (Fig. 82). The 



most conspicuous of these is the two "halves" of the bean, 



which are the seed-leaves (cotyledons) gorged with reserve 



food. These cotyledons stand upon a minute stem, which 



in the seed is curved up against them, and which is called 



the hypocotyl, a name applied to the peculiar stem of an 



embryo. Between the cotyledons, and arising from the top 



