In such leaves, there are a well-marked cuticle, a thick epidermis, a thick hypodermis at least on the upper side of the leaf, well-developed palisade tissue, and a poorly developed system of air-spaces.
Exoskeleton The outer cellular layer (ectoderm or " hypodermis ") of insects as of other Arthropods, secretes a chitinous cuticle which has to be periodically shed and renewed during the growth of the animal.
This cellular layer is called the hypodermis; it is protected externally by a cuticle, a layer of matter it itself excretes, or in the excretion of which it plays, at any rate, an important part.
The cuticle contrasts strongly in its nature with the hypodermis it protects.
The hypodermis is the immediate agent in effecting the external changes.
By histolysis certain parts of the hypodermis are destroyed, while other portions of it develop into the new structures.
The hypodermis is composed of parts of two different kinds, viz.
(I) the larger part of the hypodermis that exists in the maggot or caterpillar and is disf e b solved at the metamorphosis; (2) parts that remain comparatively quiescent previously, and that grow and develop when the other parts degenerate.
The adult caterpillar may be described as a creature the hypodermis of which is studded with Adapted from Koerschelt and buds that expand and form the butterHerder, and Lowne.
I., II., III., vomitories) the imaginal disks are to all the three thoracic segments appearance completely separated from of the larva; I, 2, 3, buds the hypodermis, with which they are, of the legs of the imago; la, however, really organically connected bud of head-lobes; f, of by strings or pedicels.
In other insects the imaginal disks are less completely disconnected from the superficies of the larval hypodermis, and may indeed be merely patches thereof.
In Endopterygota the wings commence their development as invaginations of the hypodermis, while in Exopterygota the wings begin - and always remain - as external folds or evaginations.
- Section through a portion of the lateral eye of Limulus, showing three ommatidia - A, B and C. hyp, The epidermic cell-layer (so-called hypodermis), the cells of which increase in volume below each lens, 1, and become nerve-end cells or retinula-cells, rt; in A, the letters rh point to a rhabdomere secreted by the cell rt; c, the peculiar central spherical cell; n, nerve fibres; mes, mesoblastic skeletal tissue; ch, chitinous cuticle.
The body is covered by a cuticle which is sculptured and the various markings are of systematic importance: it is secreted by a hypodermis which also includes nerve-cells and some gland-cells.
The black represents the cuticular product of the epidermal cells of the ocular area, taking the form either of))...,r,, f lens, cl, of crystalline body, cry, or of rhabdom, rhab; hy, hypodermis or epidermal cells; corn', laterallyplaced cells in the simpler stage, A, which like the nerve-end cells, vit' and ret', are corneagens or lens-producing; corn, specialized corneagen or lens-producing cells; vie, potential vitrella cells with cry', potential crystalline body now indistinguishable from retinula cells and rhabdomeres; vit, vitrella cell with cry, its contained cuticular product, the crystalline cone or body; ret', rhab', retinula cells and rhabdom of scorpion undifferentiated from adjacent cells, vit'; ret, retinula cell; rhab, rhabdom; nf, optic nerve-fibres.