Orgamzation of Leaves. 1 1 



not constant; for in the white serapias, the utriculae of 

 which arc also festooned, the pores are disposed ver)- re- 

 gularlj- .in the direction of the length of the leaf. 



Ail leaves are not in the same manner providi-d with 

 pores : some have pores on both surfaces, others have them 

 only on one ; and some are entirely destitute of them. At 

 the'cnd of this memoii- I shall give a catalogue of most of 

 the plants which I have examined, and which I have ai'- 

 ranged in three tables according to these divisions. 



Trees in general have pores only in the interior surface of 

 their leavesr Those, however, ot the fir and the larch have 

 thein on both their surfaces ; and the funiperus sablnn and the 

 common juniper exhibit pores only on the upper face. 



But pores are not found in leaves alone : they are found 

 in the seminal leaves, in most herbaceous stems, and in 

 that of the cactus JiageUiformis w Inch has no leaves ; they 

 are also dissen)inated throughout the bractcae, stipnlte, ca- 

 lyxes, and in the corolla without a calyx : I have even found 

 them in the corolla with a calyx, though in less quantity ; bvit 

 I will not assert that they are all provided with them. In a 

 word, I have observed them in the antherae, the pistils, and 

 pericarpium of the IHmm Ivlhijenim ; and I have no doubt 

 that they are found also in the parts of iTuctiticatiou of 

 other plants. 



The existence of pores in the leaves having been fully 

 established by various observations, I shall now show the 

 manner in which I found them to be formed. 



Were we to suppose that the pores are apertures formed 

 by chance in the surface of the leaves, we should be in an 

 error. Nature had some end in forming ihem, and the at- 

 tentive observer will soon perceive that it has giveii to these 

 pores a peculiar organization. Each pore indeed, when 

 observed with the microscope, seems to be placed in the 

 middle of a body nearly spherical, composed of tv^fo small 

 uniform utriculae, perfectly similar,, opposed to each other 

 by their concave faces and united by their extremities, the 

 result of which is a vacuity or interval of an oval form, to 

 which I have given the name of pore, fig. 1, 5, and 6. 



These reniform utnculse, which I t^hall call a^rijugate, con- 

 cur with the exterior utricuk? towards the formation ot t)ic 

 surface of the leaf; they are so closely united, that when the 

 pellicle is renjoved they are removed with it, except in the 

 frilillariu and aloe; which arises, no doubt, from tiie ]K'llicle 

 being formed, as already said, merel) by the !?ii}x;r»or hice 

 oi the utriculte, the lateral surfaces of vvhicli adhere to the 



parcntiiynic 



