42 ORGANOGRAPHY. BOOK I. 



quadrangular, as in Yucca gloriosa (Plate III. fig. 10.), and 

 Agave americana, and by Brown to be very rarely angular, 

 of which, however, no instance is cited by that botanist. The 

 former case is one in which the quadrangular figure is caused 

 by the cellules being straight ; I am not aware if Brown means 

 the same thing. I have never been so fortunate as to discover 

 the membrane which this great observer describes as generally 

 overlying the apertures ; nor do I know of any other botanist 

 having confirmed that observation. It cannot be the pellicle 

 already described, because it has been found that that part 

 never overlies the stomates (see page 39.) 



Nerium oleander and some other plants have, in lieu of 

 stomates, cavities in the cuticle, curiously filled up or pro- 

 tected by hairs. (See Annales des Sciences, xxi. 438.) 



A very remarkable state of the same organs occurs in Ne- 

 penthes ; in that plant there are stomates of two kinds, the 

 one oblong, semitransparent, and almost colourless, with nu- 

 merous pellucid globules in the cavity of their cells ; the other 

 roundish, much more opaque, and coloured red. The latter 

 do not communicate immediately with internal cavities in the 

 parenchyma, but are in contact with an internal deep brownish- 

 red gland, the lower side of which sometimes appears to have 

 six regular plane faces obliquely resting upon a central face, 

 or, in other cases, to be composed of six cells surrounding a 

 seventh, all being filled with dark red colouring matter. The 

 nature and use of these glands, and of the stomates that ac- 

 company them, is unknown. Something analogous to them 

 is met with in Dionaa muscipula, and jnay perhaps be con- 

 nected with the excessive irritability of its leaves. If the 

 upper surface of that plant, where the irritability exclusively 

 exists, be attentively examined, it will be found to be densely 

 covered with minute red dots, which by a little rubbing in water 

 may be separated from the cuticle. These dots are discoidal 

 glands originating iqjon roundish green stomates, bearing the 

 same relation to the stomates of Dionaa as the hexagonal glands 

 to those of Nepenthes, except that in the latter the glands are 

 below the cuticle, and in the former they are on its outside. 

 Each gland in Dionaea has a double convex form, and consists 

 of about fourteen bladders at the circimiference. It is probable 



