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toothwort

Значение термина toothwort в knolik

toothwort - Toothwort (Lathræa squamaria)
toothwort - The Toothwort is perhaps the most remarkable plant in the whole British flora, for it stands out from all other plants as a man of marked eccentricities stands out from his fellows.

Most of its life is spent in underground burrowing around the roots of trees, and in preying upon them, for it is a parasite of a most pronounced character. It forms suckers like small discs, which fasten upon the tree-roots and draw out into themselves the life juices of its host. It is not particular in its choice of trees, though apparently it avoids the conifers, while its special favourites are the hazel and the poplar.

In appearance it is most peculiar, for it consists of many thick, fleshy shoots of ivory whiteness, all crossing and inter-crossing, and filling up the spaces between the branching rootlets; in fact, a well-grown plant may completely cover a square yard. And as it grows it continually sends up new suckers and forms new attachments to its host to meet the increasing demands which its daily growth entails.

The shoots are covered by thick overlapping fleshy scales (to which it owes its Latin specific name of squamana, from squama - a scale), and these scales closely resemble human teeth both in shape and colour, hence its common name of Toothwort. Its habit of complete parasitism is responsible for its lack of green colour, for if the plant is not going to manufacture food for itself it requires no green colouring matter, since that is the special work of the colouring bodies.

But the Toothwort is something more than an ordinary parasite, and has another source of supply for its needs, though for long this was not suspected, and indeed it takes a very careful examination to reveal this side of its character. The mystery lies in the apparently solid-looking thick white scales, for they are not so solid as they appear at first sight. If we remove one we find that on its under surface, near the junction with the stem, is a little canal running across it, and into this canal open, by very minute apertures, some extraordinary winding chambers which are hollowed out in the flesh of the scale. These chambers vary in number, but the average number is ten, and, if we examine them closely with the microscope, we find that they have all over their interior two sorts of peculiar structures, one set looking like little mushrooms and the other like small domes.

Now the question comes, what can be the purpose of these most mysterious chambers? And the answer is that they are ingenious animal traps of a kind that is probably unique in the whole realm of plant life. Of course, they can only entrap animals of the most minute description - the tiniest flies, infusoria, and the like - but such as these creep into the canals from the soil and eventually slip through into the chambers. Directly they get inside they come into contact with the little mushroom and dome-like structures on the walls, and these immediately send out long filaments like tentacles, which seize and hold their prey. And very soon all that remains of the intruder, if he be a fly, is his bristles, legs and hair; if he be merely a jelly-like amoeba - nothing! All has been absorbed by the white fleshy scales. We do not know what lures the insects into these death chambers; perhaps it is adventurous exploration, but more probably it is a search for food. When we remember that there are some ten chambers in every scale, and a very large number of scales on the many branching thick stems, we can realise that the annual "catch" of insect life is comparatively very great, and, moreover, since the scales do not fall off in winter-time nor are greatly affected by the frost in their underground seclusion, the process goes on all the year round. In this way it differs from the parasitic habit of the plant, for the suckers on the roots only work when the tree is in full leaf in summer-time. When the leaves fall and the tree hibernates, the suckers wither away and sever the connection. When spring comes and the sap once more begins to flow new suckers form and the old routine commences afresh. Thus in summer-time the plant is both insectivorous and parasitic, and may be considered a gross feeder.

Now, though the major part of the plant is wholly subterranean, yet, for a short time in the spring, it sends up flowering branches above the ground. These are straight, unbranched shoots, which vary in height from three or four inches to about a foot. They also are fleshy, and they bear at their summits spikes of flesh-coloured or bluish flowers, the flowers being arranged closely together down one side of the spike. These flowering shoots are certainly striking looking, as is abundantly proved by our picture, though perhaps rather uncanny and repulsive; a lens shows that they are covered all over with glistening white hairs. Each flower has four speckled white sepals all united. The corolla is also a tube - four petals joining - and on it four stamens stand. They have thick stalks, and their heads are fringed with hairs. Inside is a white seed-case and column, and, down by the base, is a projecting yellow cushion in which honey is stored.

When the flowers first open, the column from the seed-case, bent like a hook, projects out of the corolla. The stamens are shut up in the corolla, and in any case the anthers are closed, so that if any pollen at all fertilises the projecting stigma it can only come from another older flower.

Then comes a second stage - the corolla and stamens lengthen, the column straightens and raises the stigma, the anthers open and shed their pollen; this is the moment when a visit from a humble-bee, attracted by the honey, is most opportune. He approaches, and thrusts his proboscis in search of the yellow honey-cushion, rubbing on the stigma any pollen that he may have brought with him. Now the stamen heads lower down are held together by fine hairs, while their filaments are covered with wee, sharp prickles. Therefore it behoves the insect to probe most carefully down the very centre of the flowers, as a hair's-breadth deviation means punishment by the prickles. This probing necessarily separates the stamen heads and they immediately drop their pollen on the bee. He takes his fill of honey and goes; the flower has been fertilised itself and has, moreover, sent on fertilising pollen elsewhere.

But suppose no suitable insect penetrates into the depths of those woodlands beloved by the Toothwort, and the flowers are left unvisited, there is yet more to happen. The stamens lengthen in any case and their heads no longer touch, and if the anthers are still full of pollen the slightest wind will blow away their fine powdery dust and waft it to neighbouring flowers, particularly to the younger ones with still projecting styles which are growing higher up the spike. And so these are fertilised, and we see that the plant thus makes a bid for the kind offices of both insects and the wind.

The Toothwort is closely related to the yellow rattle and the cow-wheat, both of which, though thieves, are not so to the wholesale extent that the Toothwort is. But it is even more closely connected with those well-known parasites, the broomrapes.

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stitchwort

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