THE VEGETABLE ORGANIZATION* 1^99 



tvhose interstice will be the median nerve. If other vesicles 

 be developed within these two cells, and become in their 

 turn large tertiary cells, their interstices will form the lateral 

 nerves, and will seem to derive their origin from the median 

 nerve. Other vesicles may, in the same way, be developed into 

 cells in each of the tertiary cells, and others again within these, 

 and so on indefinitely; and a primary microscopic vesicle 

 will be thus transformed almost before our eyes into the leaf of a 

 dicotyledonous plant. At the same time that this development 

 of the cellular texture of the leaf is going on, a vascular con- 

 nexion with the sap-vessels of the branchlet to which it is at- 

 tached may be formed through the medium of the hilum or 

 point of attachment of the primary cell, and with this again 

 throughout the leaf, by the hila of the secondary, tertiary and 

 succeeding orders of cells, the interstitial spaces which 

 form the nerves becoming vascular, in consequence of the de- 

 velopment of elongated cells or tubes through these points of 

 attachment. 



The structure of the floral coverings, that is of the calyx and 

 corolla, is analogous to that of the leaves; consisting of a 

 cuticular expansion, soft and pulpy cellular texture, and fibres 

 or vessels running in a longitudinal direction and ramifying so 

 as to form a kind of network, and differing from the structure of 

 the leaves chiefly in the delicacy of its several parts. But the 

 variety and elegance of their external forms, and the beauty of 

 their colours, are such as to excite our deepest admiration. 



" Not a flower 

 But shews some touch in freckle, streak, or stain, 

 Of his unrivalled pencil. He inspires 

 Their balmy odours, and imparts their hues. 

 And bathes their eyes with nectar, and includes. 

 In grains as countless as the sea-side sands, 

 The forms with which he sprinkles all the earth." 



The stamens and pistils, or those parts which are more imme- 

 diately concerned in the process of fructification, and for the 

 preservation and due elaboration of which the more conspicuous 

 parts of the flower are destined, consist apparently of cellular 

 texture only. 



The most important part of the fruit is the seed. This organ 

 consists, at least in the flowering plants, of an embryo, or the rudi- 

 ments of the future plant, and various envelopes, generally two, 

 sometimes three or four. Tlie essential parts of the embryo are 

 the plumula or young plantlet — the radicle or future root — and the 

 cotyledons or seed lobes, destined for the nourishment of the 

 other portions in the first stages of their growth. Another im- 

 portant part of the seed, though not discernible in all plants, is 

 the albumen, — that which forms the principal part of the seed in 

 the Cereales and grasses, and which, in one of this tribe, the 

 Triticum hyhernum, or wheat, is of such vast and incalculable 

 importance to the welfare of the whole human race. The 



