GROWTH OF PLANTS. 57 



A plant gains another mouth and stomach with every 

 new fibre of root, and every new leaf. 



The power which roots possess of taking up nour- 

 ishment does not cease as long as nutriment is 

 present. When the food of a plant is in greater 

 quantity- than its organs require for their own perfect 

 development, the superfluous nutriment is not re- 

 turned to the soil, but is employed in the formation 

 of new organs. At the side of a cell, already formed, 

 another cell arises ; at the side of a twig and leaf, 

 a new twig and a new leaf are developed. These 

 new parts could not have been formed had there not 

 been an excess of nourishment. The sugar and 

 mucilage produced in the seeds, form the nutriment 

 of the young plants, and disappear during the de- 

 velopment of the buds, green sprouts, and leaves. 



The power of absorbing nutriment from the atmo- 

 sphere, with which the leaves of plants are endowed, 

 being proportionate to the extent of their surface, 

 every increase in the size and number of these parts 

 is necessarily attended with an increase of nutritive 

 power, and a consequent .further development of new 

 leaves and branches. Leaves, twigs, and branches, 

 when completely matured, as they do not become 

 larger, do not need food for their support. For 

 their existence as organs, they require only the 

 means necessary for the performance of the special 

 functions to which they are destined by nature; they 

 do not exist on their own account. 



We know that the functions of the leaves and 

 other green parts of plants are to absorb carbonic 

 acid, and with the aid of light and moisture, to 

 appropriate its carbon. These processes are contin- 

 ually in operation; they commence with the first 

 formation of the leaves, and do not cease with their 

 perfect development. But the new products arising 

 from this continued assimilation are no longer em- 

 ployed by the perfect leaves in their own increase : 

 they serve for the formation of woody fibre, and all 

 the solid matters of similar composition. The leaves 



