Beneath the epidermis is a longitudinal layer of muscle-fibres which are separated into four distinct groups by the dorsal, ventral and lateral areas; these are occupied by a continuation of the epidermic layer; in the lateral areas run two thin-walled tubes with clear contents, which unite in the anterior part of the body and open by a pore situated on the ventral surface usually about a quarter or a third of the body length from the anterior end.
Doing this she bursts the epidermis of the rootlet, and her body projects into the surrounding earth.
Pression of epidermis, opening downwards.
In many forms its hyphae are particularly thick-walled, and may strikingly resemble the epidermis of a vascular plant.
This surface layer in the typically subaerial shoot of the sporophyte in Pteridophytes and Phanerogams is known as the epidermis, though the name is restricted by some writers, on account of developmental differences, to the surface layer of the shoot of Angiosperms, and by others extended to the surface layer of the whole plant in both these groups.
Sometimes the epidermis is considerably more developed by tangential division of its cells, forming a many-layered water-tissue.
The epidermis of a very large number of species bears hairs of various kinds.
Types of glands also exist, either in connection with the epidermis or not, such as nectaries, digestive glands, oil, resin and mucilage glands, &c. They serve the most various purposes in the life of the plant, but they are not of significance in relation to the primary vital activities, and cannot be dealt with in the limits of the present article.l The typical epidermis of the shoot of a land plant does not absorb water, but some plants living in situations where they cannot depend on a regular supply from the roots (e.g.
In correspondence with its water-absorbing epidermis function it is not cuticularized, but remains usually thinof Root, walled; the absorbing surface is increased by its cell~
The main assimilating tissue, on the other hand, is under the upper epidermis, where it is well illuminated, and consists of oblong cells densely packed with chloroplasts and with their long axes perpendicular to the surface (palisade tissue).
C/i, epidermis; st stoma; me,, mesophyil; pal, palisade; spa, spongy tissue; Isp, inteicellular space; wi., water tissue; x, xylem; p/i, phioem; Phil, phloeoterma; sri, scierenchyma.
In the leaf-blade this sometimes aopears as a layer of thickened subepidermal cells, tht hypoderm, often also as subepidermal bundles of sclerenchymatou~ fibres, or as similar bundles extending right across the leaf from mu epidermis to the other and thus acting as struts.
This tissue remains living and is usually formed quiti early, just below the epidermis, where it provides the first periphera support for a still growing stem or petiole.
The epidermis in the stair and the surface layer of the root soon becomes differentiated froit the underlying tissue.
The branches of the stem arise by multiplication of the cells 01 the epidermis and cortex at a given spot, giving rise to a protuber ance, at the end of which an apical meristem is established.
This consists typically of close-fitting layers of cells with completely suberized walls, intended to replace the epidermis as the external protective layer of the plant when the latter, incapable as it is of further growth after its original formation, is broken and cast off by the increase in thickness of the stem through the activity of the cambium.
In the epidermis itself (rarely), in any layer of the cortex, or in the pericycle.
Its most usual seat of origin in the stem is the external layer of the cortex immediately below the epidermis; in the root, the pericycle.
E, epidermis; q, phellogen; 1, cells, and ~1, the pheliogen of the lenticel; k, cortical parenchyma, containing chlorophyll.
The opening and closing of the stomata is the result of variation in the turgidity 01 their guard cells, which is immediately affected by the condition of turgidity of the cells of the epidermis contiguous to them.
Usually they are absent from the cells of the epidermis, though in some of the lower plants they are met with there also.
The other type is called endctropic. The fungal filaments either penetrate the epidermis of the root, or enter it from the stem and ramify in the interior.
From the outer cortical myceliuni, again, branches pass through the epidermis and grow out in the soil, In stich cases the roots of the plants are usuall) found spreading in soils which contain a large amount of humus, or decaying vegetable matter.
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.
In the epidermal cells of the leaf of species of Vanilla (\Vakker), and in the epidermis of different parts of the flower of Funkia, Ornithogalum, &c. (Zimniermann), highly refractive bodies of globular form, elaioplasts, which consist of a granular protein ground-substance containing drops of oil.
- Stinging Hair of Urtica dioica, with a portion of the epidermis, and, to the right, a small bristle (X60).
The capillaries sometimes (in many leeches and Oligochaeta) extend into the epidermis itself.
In Lanice conchilega the posterior series of nephridia are connected by a thick longitudinal duct, which seems to be seen in its most reduced form in Owenia, where a duct on each side runs in the epidermis, being in parts a groove, and receives one short tubular nephridium only and occupies only one segment.
The body wall consists of an epidermis which secretes a delicate cuticle and is only ciliated in Aeolosoma, and in that genus only on the under surface of the prostomium.
The epidermis contains numerous groups of sense cells; beneath the epidermis there is rarely (Kynotus) an extensive connective tissue dermis.
Usually the epidermis is immediately followed by the circular layer of muscles, and this by the longitudinal coat.
The clitellum consists of a thickening of the epidermis, and is of two forms among the Oligochaeta.
In the aquatic genera the epidermis comes to consist entirely of glandular cells, which are, however, arranged in a single layer.
In the earthworms, on the other hand, the epidermis becomes specialized into several layers of cells, all of which are glandular.
We have thus the replacement of a spermatheca, corresponding to those of the remaining families of Oligochaeta, and derived, as is believed, from the epidermis, by a structure performing the same function, but derived from the mesoblastic tissues, and with a cavity which is coelom.
The nervous system is embedded in the epidermis, and the pairs of ganglia are separated as in Serpula, &c.; each pair has a longish commissure between its two ganglia.
In favour of seeing in the lateral trunks and their branches a vascular system, is the contractility of the former, and the fact of the intrusion of the latter into the epidermis, matched among the Oligochaeta, where undoubted blood capillaries perforate the epidermis.
A further fact must be considered in deciding this question, which is the discovery of ramifying coelomic tubes, approaching close to, but not entering, the epidermis in the Polychaete Arenicola.
They are found one on each cephalic tentacle, and are simply minute open pits or depressions of the epidermis, the epidermic cells lining them being pigmented and connected with nerves (compare fig.
Externally is a thin cuticle; this covers the epidermis, which consists of a syncytium with no cell limits.
Salicyclic acid is not absorbed by the skin, but it rapidly kills the cells of the epidermis, without affecting the immediately subjacent cells of the dermis.
- At the base of the epidermis (which is in general ciliated) there is over the entire surface of the body a layer of nervefibres, occurring immediately outside the basement-membrane which separates the epidermis from the subjacent musculature.
In one family, the Ptychoderidae, the medullary tube of the collar is connected at intermediate points with the epidermis by means of a variable number of unpaired outgrowths from its dorsal wall, generally containing an axial lumen derived from and in continuity with the central canal.
These hollow roots terminate blindly in the dorsal epidermis of the collar, and place the nervous layer of the latter in direct connexion with the fibres of the nerve-tube.
Special thickenings of the diffuse nervous layer of the epidermis occur in certain regions and along certain lines.
Both male and female gonads consist of more or less lobulated hollow sacs connected with the epidermis by short ducts.
H, Epidermic cell-layer; mes, mesoblastic connective tissue; n, nerves; II, III, IV, V, depressions of the epidermis in each of which a cuticular lens will be formed.
The female burrows in the epidermis much as the female trap-door spider burrows in turf in order to make a nest in which to rear her young.
The disease spreads by the mycelium growing ever the epidermis of the plant.
(After de Bary.) In A several cells of the epidermis plants.