SEEDS WHICH DISPERSE AND PLANT THEMSELVES

New Zealand Mail, 29 January 1902, Page 55

SEEDS WHICH DISPERSE AND PLANT THEMSELVES

In the current issue of “Knowledge,” Mr R. Lloyd Praeger resumes the consideration of the means employed by plants to ensure a wide dispersal of their seeds. In addition to those plants which take advantage* of the wind, water and animals to disperse "their seeds, there are a great many who do their own scattering by one or another ingenious device. “Examine,” writes Mr Praeger, “a fruit of-the common dog violet. It is a little capsule formed of three sections. As it ripens it opens along the lines of junction of these, and we get three narrow boat-shaped valves spreading horizontally from the fruit stem, and each containing several seeds. The drying of these valves causes contraction. The two gunwales, so to speak; of each boat are drawn together, pressing more and more tightly on the seeds which lie between, till one by one tire seeds spring out with considerable force. . . . Some of the crane’s-bills fling their seeds to a considerable distance by means of a more complicated apparatus. The fruit consists of five separate carpels attached by their apices to a spindle. Each carpel consists of an egg-shaped pouch containing one seed, prolonged into a slender rod, the whole adpressed to tho spindle, so that' the five pouches lie in a ring' round its base. Each pouch is open on the side which is pressed against the spindle. As the fruit ripens, the mere rapid shrinking of the outer layers of the rod of the carpel causes it to rupture the tissue which attaches it by its whole length to the spindle, and it curls with a jerk, carrying up the pouch, and causing the seed to fly out of tho opening on its inner side already referred to. Lord Avebury placed fruits of the Herb Robert on his billiard table, and found that the seeds were in this manner projected to a distance of over twenty feet. Fruits of this kind have been aptly named sling fruits. Nor is it beyond the powers of certain species to undertake even the planting of their seeds. The stork’s bills (Erodium), which are closely allied to the crane’s bills or geraniums, have curious fruits, each consisting of a torpedo-shaped seed prolonged into a slender twisted rod, which terminates in a long appendage set at right angles to tho axis of tho remainder of the fruit. The seed is furnished with bristles pointing away from the unattached end; and the twisted tail is hygroscopic—veiy sensitive to moisture Now, if the seed bo held fast, ana the whole moistened, the rod will untwist, and as a result the free end will revolve like the hand of a clock. But if, as will most likely happen in nature, this revolution causes the long appendage to come in contact with some obstacle —a blade of grass, for instance —then the motion will be transferred to the seed-bearing end, which will revolve like an auger, and as a result of the lengthening caused by the untwisting of the rod, tho seed will bo forced into the ground. upward pointing bristles will come into play if tho rod dries again, tending to hold tho seed down in its place, in spite of the contraction, and to drag down the opposite end instead; another moistening will cause the seed to burrow deeper,”