220 View- of the Theory respecting Vegetation. 



to secrete into the alburnum, through passages correspondent 

 to the anastomosing vessels of the animal economy*. For as 

 the cotyledons, or seed-leaves first afforded the organizable 

 matter which composed the first proper leaves, so these, when 

 full-grown, prepare the fluid which generates other young 

 leaves, the health and growth of which are as much depen- 

 dent on the older leaves, as those, when first formed, were 

 upon the cotyledons.*!* 



The power of each proper leaf to generate sap, in any 

 given species and variety of plant, appears to be in the 

 compound ratio of its width, its thickness, and the exposure 

 of its upper surface to light, in proper temperature. As the 

 growth of the plant proceeds, the number and width of the 

 mature leaves increase rapidly, in proportion to the number 

 of young leaves to.be formed ; and the creation consequently 

 exceeds the expenditure of true sap. This therefore accu- 

 mulates during a succession of weeks, or months, or years, 

 according to the natural habits and duration of the plant, 

 varying considerably according to the soil and climate in 

 which each individual grows : and the sap thus generated 

 is deposited in the bulb of the Tulip, in the tuber of the 

 Potatoe, in the fibrous roots of Grasses, and in the alburnum 

 of Trees, during winter, and is dispersed through their foliage 

 and bark during the spring and summer.^ 



As soon as the plant has attained its age of puberty, a 

 portion of its sap is expended in the production of blossoms, 

 and fruit. These originate from, and are fed by central ves- 

 sels, apparently similar to those of the succulent annual shoot 

 and leaf stalk, and which probably convey a similar fluid ; 



* Thilosophical Transactions, 1807- t Ibid. 1805. % Ibid. 



