These seeds are richer A, Epidermal cells.
Similarly, the small amount of cuticular and of epidermal protection, and of lignification in succulent halophytes may also be related to the same circumstance.
Each stoma is surrounded by a pair of peculiarly modified Stomata epidermal cells called guard-cells (fig.
The nervous system is thus essentially epidermal in position and diffuse in distribution; but an interesting concentration of nerve-cells and fibres has taken place in the collar-region, where a medullary tube, closed in from the outside, opens in front and behind by anterior and posterior neuropores.
The crural glands, which occur in many terrestrial Arthropods, are epidermal in origin and totally distinct from the coxal glands.
The response to the action of light in diatropic leaves is, according to Haberlandt, due to the presence of epidermal cells which are shaped like a lens, or with lens-shaped thickenings of the cuticle, through which convergence of the light rays takes place and causes a differential illumination of the lining layer of protoplasm on the basal walls of the epidermal cells, by which the stimulus resulting in the orientation of the leaf is brought about.
The epidermal cells may contain chlorophyll.
The dorsal epidermal nerve-tract is continued in front into the ventral wall of the collar nerve-tube, and at the point of junction there is a circular commissural thickening following the posterior rim of the collar and affording a special connexion between the dorsal and ventral nervetracts.
Mention may be made here of a class of epidermal organ, the hydaihodea, the wide distribution and variety of which have been revealed by recent research.
Stomata are often absent, absorption and excretion of gases in solution being carried on through the epidermal layer.