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water crowfoot
Значение термина water crowfoot в knolik
water crowfoot - WATER CROWFOOT (Ranunculus aquatilis)
water crowfoot - A sheet of silver lay over the surface of the still pool; myriads of tiny silver plates, strewn over a background of darkish green, were facing the sky and catching the sunshine. For the Water Crowfoot had once again taken possession, and was making as brave a show in its own special subdued way as its gilded and more striking relatives, the buttercups, were doing on the banks around. Barring the water lily - Queen of water plants - there is probably no other plant that beautifies stream and pond more than does the Water Crowfoot, for its numberless white flowers, all centred with gold, have such a shimmering quality about them.
A plant of a particularly adaptable nature it is, too, as we discover when we examine it growing under different conditions. Thus, if we fish some of it out of the pool we find it is a network of dark floating stems with pale, short rootlets arising at points along it. The leaves float below the surface of the water and are each reduced merely to a number of fine green streamers spread out circle-wise. But in the slow-running stream beyond the pool the same plant lies in patches often, for choice, down the centre of the stream, and here the fringed leaves are no longer in circles, but, with their segments lengthened, are all lying parallel in the direction of the current. Though they look fine and delicate, yet they are tough and strong so that they are not torn by the pressure of the running water. Again, if we pick the plant by the edge of the stream or from the muddy shore of the little backwater, we find a much greater variation, for though some of the leaves - those lying under the water - are still cut up, as it were, into threads, it now bears other strikingly different leaves which rise in the air and are normally formed. That is to say, each is flat and shining, a lobed half circle of tissue. This power of producing two kinds of leaves, a leaf for the water and a leaf for the air, is the special characteristic of the Water Crowfoot. And the value of it is apparent on a little consideration. The normal leaves act with regard to the air as do other normal leaves on other plants - that is to say, they breathe in oxygen, they assimilate carbonic acid gas, and they regulate the water current within the plant. The thread-like leaves have also these functions, at any rate, the first two of them, but water is a denser medium than air, and the fact that in their thread-like development they present a much larger area and can act on a greater surface is the reason for this modification, combined, of course, with the second fact that this fringe-like formation presents no barriers to the flow of the water. Notice that just where the leaf stalk joins the main stem there are two green leaf-like structures with rounded ears (or auricles); these are the stipules, little appendages which we occasionally find in leaves.
The stalks carrying the flowers - one flower to each stalk - push up out of the water from the main stem, and not until the buds are quite clear of it do they open. Then they lay their five white petals right back well away from one another, and each shades off into yellowness towards the centre. The honey lies at the base of every petal and it is by the yellowness that the plant calls attention to the fact; a slight scent adds emphasis to the implied invitation.
When the stamens are mature the pollen boxes open and shed their pollen on to the petals, and there it lies until it is carried away either by the wind or by visiting insects. Anyone who has watched a swarm of little flies hovering over the surface of water in the evening time can appreciate how large a chance the Crowfoot has to entertain fly-visitors. Perhaps the flower is white because it is all the more conspicuous as evening falls; in any case, from the paleness of its petals one may compare it to a white target where the inner rings are yellow and the bull's-eye pale green. The bull's-eye is really a globular head of loosely-packed carpels each containing a single seed; as it swells in ripening we see that each carpel is very much the shape of a segment of an orange, with the inner edge straight and the outer convex. This floral bull's-eye, like the bull's-eye of a target, is the centre for all operations, and just as the shot must strike it in the target, so the pollen must strike it in the flower for the aim to be duly accomplished.
Another proof of the adaptability of the Water Crowfoot is shown when, from floods or other reasons, the water rises above its normal level, and submerges the flower-buds; for then they never open, but, inside the sheltering bud-leaves and unharmed by the water, the stamens shed their pollen upon their own ovules and seeds are duly formed in dry security.
It has been often asserted that this plant, from its nutritive qualities, might with advantage be used as fodder; in fact, old books on botany constantly record instances of its serviceableness in this direction. Curiously enough the Water Crowfoot is entirely free from poisonous and acrid juices, although such juices are commonly found in other members of its family.
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