40 SYLVA AMERICANA. 



its full magnitude'; when the embryo of a future plant may be 

 discovered in the centre of its own supplies. By this process 

 the pericarp, in a diversity of shapes and forms, is rendered 

 perfect in all its several parts ; and as the seed, which it contains, 

 is one of nature's greatest resources in the vegetable world, it is 

 defended above all other parts of the plants against the accidents 

 to which it may be liable. Thus in the one instance, it is 

 imbedded in the soft pulpy substance of the esculent fruits ; in 

 another, it is protected by thick membranes, and inclosed in a 

 pod, as in leguminous vegetables; while in a third it is surrounded 

 by a hard shell or a thick cuticle, (as in the various species of 

 corn), which requires a very strong force to rend it asunder. It 

 is thus fitted for the purpose of future germination, which will be 

 hereafter considered. 



Of the Seeds. 



The seeds are the sole end and aim of all the organs of 

 fructification. Every other part is in some manner subservient 

 to the forming, perfecting, or dispersing of these. A seed 

 consists of several parts, some of which are more essential than 

 others, and of these we shall give a particular description. 



The embryo, or germ is the most essential of all, to which the 

 rest are wholly subservient, and without which no seed is perfect, 

 or capable of vegetation, however complete in external appear- 

 ance. It is sometimes called corculum, or little heart, punctum 

 vitce, or speck of life, and it is in the point whence the life and 

 organization of the future plant originate. In some seeds it is 

 much more conspicuous than in others. The walnut, the bean, 

 pea, lupine, &c. show the embryo in perfection. Its internal 

 structure, before it begins to vegetate, is observed by Gaertner to 

 be remarkably simple, consisting of an uniform medullary sub- 

 stance, inclosed in its appropriate bark or skin. Vessels are 

 formed as soon as the vital principle is excited to action, and 

 parts are then developed which seemed not previously to exist. 



The cotyledons, or seed lobes, are immediately attached to the 

 embryo, of which they form, properly speaking, a part. They 



