42 
ORGANOGRAPHY. 
BOOK I. 
quadrangular, as in Yucca gioriosa (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 othe)' 
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 Dionaea muscipula, and may 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 upon roundish green stomates, bearing the 
same relation to the stomates of Dionaea as the hexagonal inlands 
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 circumference. It is probable 
