54 
ORGANOGRAPHY. 
BOOK I. 
chyma, 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 wdth dark red colouring matter. The 
nature and use of these glands, and of the stomates that ac- 
company them, is unknown. This is I believe the only case 
hitherto noticed, where the same species has stomates of dif- 
ferent forms ; it is also remarkable, because in one of these 
cases the stomate does not open into a chamber of the paren- 
chyma, but immediately reposes upon a gland. 
Although the usual condition of stomates is such as is above 
described, yet there are cases in which it is materially mo- 
dified, and their function is changed. An instance of this 
occurs in Dioneea muscipula, in which the peculiar glands, 
placed in great numbers on the upper side of the lamina of 
the leaf, each proceed from a pair of parallel green cells, 
apparently of the same nature as the two cells forming the 
sphincter of a stomate. 
In the epidermis of certain plants are openings resembling 
stomates, which require to be distinguished from them. In 
Nuphar luteum they occur in the form of circular depressions 
{Jigs, a and 5), the sides of which are marked by ele- 
vated rings. In Peperomia pereskiaefolia {Jig. e) they are 
deep impressions in the epidermis, at the bottom of which 
is a two-celled hair. These have been taken for stomates by 
Meyen, in a plant called by him Pleurothallis ruscifolia 
{Wiegman's Arch. 1837. t. 10. Jigg. 4, 5, 6, 7, 8, 9.) ; but ac- 
cording to Schleiden, the observations of this anatomist are 
incorrect, and all such appearances are either spaces left by 
the fall of hairs, whose bases fitted into the cavity, or formed 
for the reception of hairs, or depressions of entirely a different 
nature from stomates. 
Stomates are not found in Mosses, Fungi, Algae, or Lichens 
(see Introduction to the Natural System ) ; in no submersed plants, 
or submersed plants of amphibious plants. They are not 
formed in the cuticle of plants growing in darkness, nor upon 
roots, nor the ribs of leaves. It frequently happens that they 
are found upon one surface of a leaf, but not on another, and 
