64 VEGETABLE ORGANOGRAPHY. 



obtained; — that the lines which are obser\:ed on it are the 

 traces of cellules, sometimes very different from the 

 ordinary ones, and sometimes very much resembling 

 them • — lastly, that it can only be completely seen by a 

 transverse section of the leaf. The same reasonings are 

 so clearly applied to the cuticle of petioles, young 

 branches, the calyx, corolla, fruit, and, in general, of 

 all the organs examined in the state of their first deve- 

 lopment, that I do not know how to admit another 

 opinion. We shall see presently that old trunks present 

 entirely different phenomena. 



Let us examine, for the present, the Cuticle, consi- 

 dered as a peculiar membrane. 



The Cuticle does not appear to be a simple membrane, 

 as it seems from a common inspection, or even under most 

 microscopes, when it is removed from the surface of the 

 leaf; but it appears formed of a row of flattened cellules, 

 distinct from those of the parenchyma, as Amici has dis- 

 tinguished by the aid of his powerful microscope, and as 

 I have seen in Tritoma Uvaria with weaker instruments. 



This membrane is generally more tenacious and com- 

 pact than that of the ordinary cellules of the parenchyma ; 

 which may result either from its pecuKar nature, or from 

 the action of the air, light, or evaporation : this last cause 

 appears to be the principal ; for — 



1st. The cuticle is much more compact when it has 

 been some time exposed to the aii', than when it is first 

 developed; wherefore it has been said of certain very 

 fugacious organs, that they are devoid of cuticle. 



2d. The cuticle, furnished with stomata, is generally 

 more compact, and, consequently, more easily separable 

 from the subjacent tissue, than that which has none, and 

 which appears less endowed with the faculty of evapo- 

 ration. 



3d. We know that the water which arrives at the 



