kidney vetch defined in 1913 yearkidney vetch - Kidney Vetch (Anthyllis vulneraria);
kidney vetch - The Kidney Vetch, after all, is not really one of the Vetches in spite of its name. It is true that it belongs to their family - the Leguminoseæ - but it is not included in the Vicia, or Vetches, group of that family. It has not the tendrils that the vetches have, and its stamens are all joined together into one bundle, instead of the top stamen being free, and so leaving a gap in the filament tube, as is the case in its name-sakes. In fact, the Kidney Vetch has a unique personality of its own in various directions, and stands quite alone as the sole representative in our flora of the genus Anthyllis, a genus that at the best is but small, its twenty or so species being confined to the north temperate region of the Old World.
It is a low herb, from a few inches to a foot in height, and is often half sprawling on the ground. It loves the tops of cliffs, both sandstone and chalk, as well as the dry pastures of the chalky downs. Its foliage is not very much in evidence in the low herbage among which it dwells, for each leaf is cut up into a number of very narrow leaflets. The terminal leaflet is much longer and somewhat wider than the lateral ones, while the latter are often arranged very unevenly. But if the foliage is insignificant the flower clusters in June and July are very striking and quite unmistakable, for these consist of some fifteen to twenty flowers apiece, gathered into close heads, each head being set in a big, circular, green ruff formed of a single green bract which is cut deeply into many lobes. The fact that these close clusters - "spoky rundles," in Gerard's quaint phraseology - are somewhat kidney-shaped no doubt accounts for the "Kidney" in its common name, albeit Lyte, in his "Niewe Herball" of 1578, says that the plant owns its name because "it shall prevayle much against the strangury and against the payne of the reynes." But other herbalists do not generally appear to endorse this statement. Gerard specially says it is "not used in meate or medicine that I know of," and, probably, as was so often done in those illogical days, Lyte argued the cure from the name, and not the name from the cure. Nevertheless, the plant had a definite reputation as a staunch-wound, and we have on record that at the beginning of the eighteenth century it was publicly sold for this purpose in the market at Dublin under the name of "Stanch." From this reputation, its specific botanical name of Vulneraria (Latin, vulnus, a wound) was derived also its old English names of "Stanch" or "Staunche," and "Woundwort."
If we look closely into the "spoky rundles," we see that each of the fifteen to twenty stalkless flowers has a bright yellow pointed end passing back into a long, woolly tube. "They look like lambs' tails," say the country children, and so as "Lambs' Tails" they are often known. Likewise as "Ladies' Fingers," with perhaps a reference to such fingers in warm winter mittens, though this name is sometimes attributed to the presence of the spreading palmate bract at the back of the flower-clusters. As we pick out individual flowers from their setting they feel warm and woolly to the touch, this being due to the coat of soft, white hairs that so thickly envelops the calices. Though the whole plant is covered with a slight down, it is these calices that are the "downiest" part, and it is they that account for the name Anthyttis, which is derived from two Greek words signifying "flower" and "down." Since each calyx is somewhat inflated, it is a prominent part of the flower. The value of this down to a low herb is obvious. It prevents small insects from roaming at will over its surface - or, at any rate, makes it very difficult for them to do so. The petals are five, yellow just where they show beyond the calyx, but continuing back into the calyx tube as long, narrow, white limbs. It is rather as though they were all on stilts. The big, upper petal turns back with upstanding flap; at the base of this flap, on either side, are two curved arms, very like those of an arm-chair, and these arms embrace the waist of the rest of the flower. The two side petals, or wings, are closely pressed together and enfold two still smaller ones which form the keel. At the base of the yellow portion of the wings, and on the upper side, are two fine hooks which need careful looking for. These fit into folds on either side of the keel and interlock these two portions of the flower. The keel wraps up the upper part of the ten stamens whose filaments are all joined to form a long white tube, though their heads are distinct. The pollen from these heads must necessarily fall into the cavity of the keel. At the base of the calyx lies a minute, green pod, very flattened and almost circular in outline, and from it a long style runs to the farthest point of the keel.
Now, since the tube of this flower is unusually long all short-tongued insects are barred from visiting it to any advantage to themselves; only butterflies and long-tongued bees can reach into its recesses to get the honey present. They alight upon the saddle ridge formed by the interlocked wings and keel, their weight depressing it. As the keel "gives," the pollen lying loose within is forced out through its apex by the stamens and style acting as a piston, and the grains scatter over the insects' abdomens and legs. Under a lens these grains can be seen to be all short, six-sided prisms with striated angles. When the flower is young the top of the style - the stigma - is quite dry, so that none of the pollen adheres to it, and the explosion may occur several times over. But as the flower ages and becomes limper, eventually the keel is depressed to such an extent that the style shoots out through the orifice and itself strikes the insect. By this time it has become moist and sticky from being rubbed, and it will gather on itself any pollen that may be on that insect at the point it strikes. This will almost certainly be pollen from another neighbouring flower, since its own pollen will have been dissipated by the previous explosions. The whole arrangement is a very neat one. We saw a similar one in the bird's foot trefoil (Lotus corniculatus).
Among the flower's visitors a certain beautiful little blue butterfly, by name Polyommalus Hylas, is particularly constant and appreciative, but she finds a special purpose for our Kidney Vetch, for she lays her eggs in the ovary when she visits, and thus makes an exchange for her own ends when she flies off as carrier of the flower's pollen. The eggs produce caterpillars, which find food in the immature seeds by their side. Later they crawl out and retire below ground, and there remain for their chrysalis stage - and, indeed, until they emerge in their full glory as dainty blue butterflies. The flower contains no honey, and has no appreciable scent; it relies, therefore, upon its masses of colour for attractive power.
As the flower fades, its petals change from yellow through orange to brown, and this colour change gives the Kidney Vetch in the mass a still more striking appearance, for yellow, orange and brown clusters rank side by side. The calyx becomes even more inflated, and within, as in a bladder, the tiny pod ripens. Eventually the dried-up clusters disintegrate, and the individual parts fall to the ground; the wind catches the hairy, dry calyx bladders and hustles them about, and thus their contents - the pod with its usually single seed - get dispersed.
The Kidney Vetch bears on its roots in a marked degree those little nodules which we now know are the dwelling places of bacteria. These bacteria receive benefit from, and return benefit to, the plant. They receive a home, and in return they take free nitrogen from the air and pass it on after combining it in such a way that the plant can use it in its physiological processes. Were it not for these bacteria the great reservoir of free nitrogen in the atmosphere would be sealed to the plant, and it would have to rely entirely upon the soil for the supply of its necessary nitrogen. It is because these bacteria colonies frequent the roots of many of the members of this family of the Leguminoseæ, such as peas, beans, bird's foot trefoil, etc., that these members can actually enrich the land in which they grow instead of impoverishing it. It has been suggested at various times that the Kidney Vetch should be cultivated as a fodder plant, and it does appear to be very acceptable to cattle and a good pasture, but the suggestion seems never to have been taken up seriously.
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near kidney vetch in Knolik
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