86 VEGETABLE ORGANOGRAPHY. 



curticaux), but these organs must not be confounded 

 with the Stomata, which are Hkewise called Cortical 

 Pores. In order to avoid this confusion, it seems to 

 me more advantageous to employ a distinct name for 

 each organ. The change of form of the Lenticels is the 

 most remarkable circumstance which they present at 

 first sight : these changes are especially visible in trees 

 the bark of which remains a long time smooth — as the 

 Cherry and Birch ; the Lenticels are here seen in the first 

 year oval in a longitudal direction, very small, and 

 scarcely visible ; afterwards the distension of the branch, 

 by its increase in diameter, renders them rounder and 

 larger; in proportion as the distension continues, they 

 become more oblong transversely, and finish by forming 

 kinds of horizontal, and often very distinct lines: on the 

 contrary, when the bark of trees is cracked or split, they 

 disappear very rapidly. In Cineraria prcecox, which 

 has a fleshy bax'k, the lenticels are very large, and preserve 

 an orbicular form during the whole life of the plant. 



These organs exist in the bark of almost all Dicoty- 

 ledonous trees, except the ConiferEe, Roses, &c. They 

 are generally absent in herbaceous Dicotyledons ; Vau- 

 cher, however, has observed them in Malva sylvestris and 

 Samhucus ehulus. No vestige of them is ever found 

 either in Monocotyledons or A cotyledons. It is from 

 the lenticels that the roots to which the branches give 

 origin arise, either naturally in the air, as in Rhus, 

 Flcus, &c. (PI. 6.*) or when they are produced either in 

 \vater or a moist soil, as in layers and cuttings. When 

 the lenticels have been removed, and most probabl}^ 

 when they are wanting, or are not developed, adventi- 

 tious ones are formed on the branches under favourable 

 circumstances, and these give origin to roots just as the 



* This represents the roots proceeding from the lenticels of Ficus eiastica. 



