612 CONSERVATIVE ORGANS. [LECT. XI. 



tions ; and occasionally a double ring, with the in- 

 tervening space, also, divided into four or more 

 equal parts: examples of the first variety are found 

 on the lower disk of the leaves of Lilac (61. p. 

 611), of Acuba Japonica (6^.), Cussonia thyrsi- 

 flora (63.), Hoya carnosa (fig. 3, Plate 10) ; and 

 on the upper disk of the leaf of Rumex ace- 

 tosa (fig. 9, Plate 10). The upper disk of the 

 leaves of Viola odorata affords an excellent illus- 

 tration of the double ring (64.). But the most re- 

 markable form of the cuticular pore, which I have 

 yet observed, is found on the back of the leaves 

 of common Oleander, Nerium Oleander. It ap- 

 pears, on a superficial view, a simple oval aper- 

 ture without any shield, but guarded by hairs 

 which cross it in different directions (65. a. .); 



and is comparatively much larger than any of the 

 other kinds of pores. 



Some writers have ventured to assert, that no 

 apertures are found in those plants which are 

 generally regarded as composed almost entirely 

 of cellular matter, among which Marchantia is 

 usually reckoned ; but the incorrectness of this 

 opinion can be easily proved, by placing a small 



