CHAP. II. 



CUTICLE. 39 



no means uncommon ; he even thinks it is present in sub- 

 mersed leaves, and imagines that it overlies the stigma in 

 some plants. I, however, find nothing very definite in 

 regard to this, except that the pellicle often exists, and that it 

 does not cover the stomates. 



2. Of Stomates. 



In most plants the cuticle has certain openings of a very 

 peculiar character, which appear connected with respiration, 

 and which are called Stomates, or Stomata. (Plate III. passim.) 



Stomates {Pores of the epidermis ; Pores corticaux, allonges^ 

 evaporatoires., or grands pores ; Glands corticales, miliaires, or 

 epidermoidales ; Glanduloi cutanece ; Oeffniingen ; Stomatia ;) 

 are passages through the cuticle, having the appearance of 

 an oval space, in the centre of which is a slit that opens or 

 closes according to circumstances, and lies over a cavity in the 

 subjacent tissue. 



There is, perhaps, nothing in the structure of plants upon 

 which it is more difficult to form any satisfactory opinion 

 than these stomates. Malpighi and Grew, the latter of whom 

 seems first to have figured them (t. 48., fig. 4.), call them 

 openings or apertures, but had no exact idea of their struc- 

 ture. Mirbel also, for a long time, considered them pores, and 

 figured them as such ; admitting, however, that he suspected 

 the openings to be an optical deception. De Candolle enter- 

 tains no doubt of their being passages through the cuticle. 

 He says their edge has the appearance of a kind of oval 

 sphmcter, capable of opening and shutting. The membrane 

 that surrounds this sphincter is always continuous with that 

 which constitutes the network of the cuticle : under the latter, 

 and in the interval between the pore and the edge of the 

 sphincter, are often found molecules of adhesive green matter 

 {Organogr. i. 80.) ; and recently Adolphe Brongniart, in his 

 beautiful figures of the anatomy of leaves, would seem to have 

 settled the question beyond all dispute, {Annales des Sciences, 

 vol. xxi.) Nevertheless there are anatomists of high reputation 

 who entertain a direcdy opposite opinion ; denying the ex- 

 istence of passages, and considering the stomates rather in 



d4 



