616 CONSERVATIVE ORGANS. [LECT. XI. 



filled with air, although it is closely surrounded 

 by the oblong cells (e.) of the parenchyma, turgid 

 with green juice. In the oblong section, also, of 

 this aperture (67.) the vesicular ring (f.) does 

 not appear to be simple as in Dianthus, but is 

 divided by a duct, in which the aperture (a.) 

 seems to terminate, and which apparently opens 

 into the air cell (f. 66.) ; which is cut away in 

 this section (6?.)- 



In the leaf of Oleander the aperture (d. 68. p. 

 615) expands into a kind of sac where it pene- 

 trates into the substance of the parenchyma (c.) ; 

 and it is throughout lined with the same kind of 

 hairs which guard its orifice ; but I have not been 

 able to determine whether its lining membrane, 

 which is a production of the epidermis (a.), be 

 porous ; although I have examined it by glasses of 

 the highest powers. I may here remark that the 

 section of this leaf displays an example of a cutis 

 consisting of four layers of cells (b.). Decandolle 

 considers that the cuticular apertures are con- 

 nected with the ultimate ramifications of the ves- 

 sels of the leaf* ; and, if it be true, that the cu- 

 ticular meshes are formed by lymphatic vessels, 

 which terminate on one hand in the larger vessels 

 of the leaf, and on the other, in the vesicular 

 circles surrounding the fundus of the aperture, 

 this opinion must be correct. 



* Journ. de Phys. iii. p. 130. 



