THE CINCINNATUS. 



VOL. 11. MAY 1, 1857. NO. 5. 



THE LEAF— ITS FUNCTIONS, Etc. 



There remains, in order to complete the series of brief articles on 

 Vegetable j^bysiology proposed by us at this time, the subject of the 

 leaf and its functions. And lest we may in these scientific discus- 

 sions be called tedious, by the practical farmer, we will endeavor for a 

 time to give place to matter which may be regarded by him as more 

 immediately suited to his daily manipulations and duties. This 

 will not however be to the exclusion of what may be styled scientific. 

 For with true progress there must be science. There must be deep 

 and profound research, often leaving in the dark the superficial and 

 unthinking multitude. 



The leaf may be described as a lateral expansion of the bark and 

 intimately connected with the inner axis of the stem. 



The outer surface is called the epidermis or cuticle ; the internal 

 part, i\iQ parenchyma. Leaves at first are mere projections of cellular 

 tissue compactly united together, and finally assume a permanent 

 form and position along the axis. Whenever a leaf bud is formed, 

 a leaf is, also ; this, if not entirely developed, is at least rudimentary. 

 The manner in which leaves are coiled up difi'ers in different kinds 

 of plants. Sometimes they are folded up lengthways, sometimes 

 from above, downwards, at other times they are plaited like a fern, or 

 rolled up in a spiral form. They generally lie in a horizontal direction 

 with the plane of their surface. 



Two essential modifications of the leaf have been observed, accord- 

 ing as it is to live in air or in water. Aerial leaves have a skeletal 

 vasculal tissue, in the form of veins, ribs, or nerves ; the space be- 

 tween being filled up by a cellular tissue — the parenchyma, invested 

 by the cuticle or epidermis. This cuticle generally diifers on the two 

 VOL. II., V. — 13. (193) 



