and those parts of aquatics which are submersed, are destitute 
of stomata. They are absent in many parasitic plants: 
mosses, mushrooms, sea-weeds, and lichens also =ppem 
have no stomata. 
77. It is considered by some eminent vegetable an 
that the stomata are not perforations, but simply sisi 
more transparent spots, while others describe them as g) 
78. The cuticle protects the parts beneath from the 
direct action of air and water, and prevents too great 
ration of the fluids. It affords little protection from 
tion of heat or cold, except when covered by a thick 
or wool, as in the great mullein. In young shoots 
stems it is distinct and entire: but is soon distended, 
and pushed off: and dead layers of bark occupy its place 
79. “ In forest trees, and in the larger shrubs, the b 
of which are firm and of a strong texture, it is a part of 
importance: but in the reeds, the grasses, canes, 
plants having hollow stalks, it is of great use, and i 
ingly strong: and, by the microscope, seems compo 
kind of glassy network, which is principally siliceous 
This is the case in Wheat, in the Oat, in different spé 
_ Equisetum, and, above all, in the Rattan, the e 
_ which contains a sufficient quantity of flint to give light 
_ struck by steel. The siliceous epidermis serves as 
protects the bark from the action of insects, and_ 
perform a part in the economy of these feeble 
tribes, similar to that performed in the animal ki 
the shell of the crustaceous insects. I have 
experiment that siliceous earth generally exists | 
_ dermis of the hollow plants.”* The Bamboo (1 
bos) contains much silica, called “ tabasheer.” 
of some orchideous plants, the epidermis is ext 
+ Sir Humphrey Davy's Agricultural 
