Tophthora infestans passing K, Germination of the zoospores through the stomata D, on formed in the sporangia.
The stomata serve for all gaseous interchange between the plant and the surrounding air.
The pores of the water-stomata are the outlets of the hydathode.
Stomata are often absent, absorption and excretion of gases in solution being carried on through the epidermal layer.
Many xerophytes are hairy or have sunken stomata which may be further protected by partial plugs of wax:
The stomata are frequently in grooves: the leaves are frequently rolledsometimes permanently so, whilst sometimes the leaves roll up only during unfavourable weather.
Their stomata are frequently not limited to the underside of the leaves, but may occur scattered all over the epidermal surface.
The whole arrangement has a strong resemblance to the lacunae, mesophyll and stomata, which form the assimilative and transpiring (water-evaporating) apparatus in the leaves of flowering plants.
At intervals it is interrupted by pores (stomata) leading from the air outside to the system of intercellular spaces below.
The lenticels of the stem are usually formed beneath stomata, whose function they take up after the stomata have been ruptured and cast off with the rest of the epidermis.
This system of channels is in communication with the outer atmosphere through numerous small apertures, known as stomata, which are abundant upon the leaves and young twigs, and gaseous interchange between the plant and the air is by their assistance rendered constant and safe.
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.
Sclerophyllous leaves are ually characterized by entire or sub-entire margins, a thick cuticle, riall but rarely sunken stomata, a we1l-developed and close-set ilisade tissue and a feeble system of air-spaces.
Switch plants, such as Retama Retam and broom (Cytisus scoparius), have reduced leaves and some assimilating tissue in their stems; and stomata occur in grooves on the stem.
It is possible, however, that the absence of sunken stomata, and the occurrence of some other halophytic features, are related merely to the succulent habit and not to halophytism, for succulent species often occur on non-saline soils.
The lower surface of the potato leaf is furnished with numerous organs of transpiration or stomata, which are narrow orifices opening into the leaf and from which moisture is transpired in the form of vapour.
' ing longitudinal ridges, generally on the upper face; the stomata are in lines in the intervening furrows.
The rolling up acts as a protection from too great loss of water, the exposed surface being specially protected to this end by a strong cuticle, the majority or all of the stomata occurring on the protected surface.
The characters of leaves most useful for diagnostic purposes are the position of the stomata, the presence and arrangement of resin-canals, the structure of the mesophyll and vascular bundles.
The stomata are frequently arranged in rows, their position being marked by two white bands of wax on the leaf-surface.
The pinnae, except in a few filmy forms, are thick; in Kaulfussia large pores derived from stomata occur in the epidermis.
Stomata of the same structure as in Equisetum have been detected in the epidermis.
The latter shows marked xerophytic adaptations; the single vascular bundle was surrounded by a sheath of short tracheides, and the stomata were sheltered in two deep furrows of the lower surface.
Professor Nathorst, as the result of a more recent examination of Heer's specimen, found that the segments of the frond are characterized by the presence of two parallel veins instead of a single midrib, with a row of stomata between them; for this type of Cycadean leaf he proposed the generic name Pseudocycas.
The structure of the stomata of the sporophyte of vascular plants is fundamentally the same as that of the stomata on the sporogonium of the true mosses and of the liverwort A nihoceros.
The latter ultimately reaches the external air by diffusion through the stomata, whose dimensions vary in proportion as the amount of water in the epidermal cells becomes greater or less.
The entry of gases into, and exit from, the cells, as well as the actual exhalation of watery vapour from the latter, take place in the intercellular space system of which the stomata are the outlets.
The spot or patch is an area of injury; on (or in) it the cell-contents are suffering destruction from shading, blocking of stomata, loss of substance or direct mechanical injury, and the plant suffers in proportion to the area of leaf surface put out of action.
These adaptations tend to lessen the amount of transpiration by protecting the stomata from the movements of the air.
Stomata occur on both surfaces of the leaves, and, with the peculiar hair structure render the microscopic appearance of the plant highly characteristic.
The habitats which they affect are the hot, dry regions of tropical America, the aridity of which they are enabled to withstand in consequence of the thickness of their skin and the paucity of evaporating pores or stomata with which they are furnished, - these conditions not permitting the moisture they contain to be carried off too rapidly; the thick fleshy stems and branches contain a store of water.
Where stomata of peculiar form occur in the epidermis, while subepidermal strands of sclerenchyma occupy the ridges.
2, p), leaving air-spaces between them, which communicate with stomata; on this account the tissue has received the name of spongy.
The flat surface is spread to allow the maximum amount of sunlight to fall upon it, as it is by the absorption of energy from the sun's rays by means of the chlorophyll contained in the cells of the leaf that the building up of plant food is rendered possible; this process is known as photo-synthesis; the first stage is the combination of carbon dioxide, absorbed from the air taken in through the stomata into the living cells of the leaf, with water which is brought into the leaf by the wood-vessels.