AN INTERESTING WEED.

Temuka Leader, Volume I, Issue 89, 23 October 1878, Page 2

AN INTERESTING WEED.

Among the things not generally known Is the fact that one of the commonest of our roadside weeds belongs to that very interesting class of plants, the insectivorous. Tiie plant referred to is often called duckweed, but it is not quite the. same with the weed so cajrf , which grows in thick succulent masses in our gardens. The insectivorous plants differ widely in the complexity of the mechanism by means of which they effect the capture and assimilation of their living prey. The mechanism of this weed is perhaps simpler than that of any other of the class. It consists of short, fine hairs of two kinds, thickly distributed over the stems, leaves, ami buds of the plant. Oue of these kinds ; s short, and of almost uniform thickness. At the tip of each hair is a minute globule of a sticky fluid. The other kind of hair is considerably longer, and has no viscid globule, but tapers off to an extremely fine point. The two kinds are distributed in different proportions on different parts of the plant. On the main stems the shorter globulebearing hairs predominate, on the secondary stems and flower-huds they are seen in about equal proportions, while the leaves are mainiy, but not wholly, occupied by the longer, pointed hairs. The prey of this plant consists of very small forms of life, the smallest of midges are often captured, but. insects so large as a sand-fly never. Their most frequent prey is the minute leaping beetle that one may notice aligjjtingou one’s hands or clothes when sitting on the ground. This little creature is not much larger than the dot of an i. Its construction tends to render it u common and easy prey to the plant. Its leaping powers bring it into violent contact with the upper and more tenacious globules, while the arrangement of its limbs prevents it making effectual efforts to escape. The process of capture is comparatively simple, and is quite easily understood. The process of assimilation is not so readily ascertained. There is none of that folding over of parts to enclose the prey that other insectivorous plants exhibit. There is no further alteration of the position of parts other than is brought about by the struggles of the captive insect. The position, however, of the dried remains of insects suggests the manner in which its softer substance has been drawn from it. Generally, if not always, the shrunk skin is found transfixed upon one or more of the longer, sharply-pointed hairs. From this it would seem that the captive, in its struggles to get free, impales itself upon the points of these. A fair inference is that these pointed hairs are tubes through which the plant sucks the juices of the insect, and perhaps after a process of. digestion, a portion of its solids. It is noteworthy that where this plant is^much overshadowed by other vegetation it is not provided with the sticky hail's, and therefore is not capable of capturing prey. A few specimens may be found in exposed situations not so provided, but they are comparatively rare. Occasionally one half of the bi'anches of a stem will be so provided, and the other half not. Generally speaking, the individuals in which the insect-catching apparatus' is fully developed never attain the size and luxuriance of .those-devoid of the apparatus, A wonderful thing is that that the plants that are capable of catching prey are enabled to dispense with tbo Wrnation of flowers‘in producing seed. The flower-.

bud opens to disclose the seed-vessel full of perfect seeds. Fructification in the ordinary 1 way may, however, have taken, place, for pistil and stamens —the necessary organs—were present in the very young bud. Petals rarely appear, and when they do are imperfect—mere abortions. Tiie indiduais not fitted to capture prey produce a pretty little white flower in the ordinary way. It is certain that the capture of visible forms of animal life is not necessary to enable the plant to dispense, with tne production of a full flower, for a large proportion of the plants do not get an opportunity to exercise their powers. But it is probable that, through the medium of the liquidtipped hairs, some valuable substances are obtained from the surrounding air, either of a gaseous nature or in the shape of microscopic organisms. The air is, we know, full of the latter, and it may well be believed that these weeds obtain considerably more animal food from the x w / multitude of these minute forms than from the bodies of the visible insects. This lowly weed will probably not be so interesting to the ordinary observer as other insectivorous plants, for the reason that its mechanism is composed on so small a scale and captures prey so minute that magnifying power is necessary to observe it all ; but to the thoughtful mind it offers problems and suggestions as extensive and important as do the more striking members of this most peculiar class.