SCHOOL IN THE OPEN.

Star (Christchurch), Issue 17871, 12 June 1926, Page 24 (Supplement)

SCHOOL IN THE OPEN.

M2 i STUDIES IN THE GREAT OUT-OF-DOORS, S

(By i

J. J. S. Cornes,

8.A., B.Sc.)

jyj=! The ** Star ** has arranged with Mr T. J. S. Comes, 8.A.. B.Sc.. to J? write a series of illustrated articles which will give teachers and Is a]§ others a fuller appreciation of the Great Out-of-doors. They will |S M deal with various aspects of plant and animal life, as well as with Krg jSj inanimate nature. Questions and material for will |jg £j| be welcomed. |g

SEED SCATTERING. (CXX) The leaves have fallen from horsechestnuts, sycamores, ashes, and silverbirches. The trees stand hare, apparently dead. But looking closer we see only preparations for the years to come. X*ot only are the naked branches covered with buds, but high overhead the tender ash, though she lost her leaves so early, still rustles her bunches ot kt v like fruits, and still the gardens are beautiful with red fruit-sprays on hawthorn and flowering apple. There are many signs to remind us that all the autumn past, while man was harvesting and gathering into barns, Nature, where left to herself, has been scattering abroad and sowing. For seeds must l>c scattered as well as sown. It is important that what is sown should be carried away from the shadow of the parent plant, or away from a crowded area. It is well that the family should scatter, even though some be lost altogether, and others be borne into unsuitable places. There are some interesting points in i connection with this scattering of seeds. ; First, where seeds are scattered by a hairy “pappus” or by an insect-like

wing, the parachute mechanism ir either case is usually not on the seed itself, but on the outside of a seed-bo.x

containing: only one seed, that is on ; the outside of a nut or nutlet, for example, sycamore and ash, or dandelion and clematis. For usually where there are many seeds in a seed-box, and where therefore the seed-box. must split open to scatter its seeds, the seeds thus shed have no parachute to aid in their dispersal, for example, peas. in their pod. There arc. however, some exceptions to this rule. The common little willow-herb, Epilobium, sheds from its seed-box many small seeds each having a hairy aril. In our native bush there is a common vine, the. climbing jasmine. Parsonia, or Kaiku. with pods somewhat, like those of butterbeans. This on opening sheds many seeds that fly- away on just such hairy parachutes. Then again, in the conifers, such as pines, firs, larches, cedars, cvpresses, the wing where present must be borne on the outside of the seed itself, for such trees do not enclose their seeds in seed-boxes, but bear them naked on the surfaces of the scales of the cone, protected simply by the scales above and below. Another interesting little point is that wherever the parachute mechanism is a wing, the nutlet is borne on n fairly high tree, e.g., sycamore, ash; because such a heavy parachute needs a lofty “taking off” place. A plant much less tall requires a lighter hairy pappus, and that is why we find this stvie of parachute on the dandelion Of course,, where the little nutlets are bur-like, and intended to be dispersed in the fur of passing animals, the plant will also l>e found to be a low one—for instance, bid-a-bids, cleavers in the hedges, or the little sedge Uncir.ia in the bush. A very interesting example of the distribution of little nutlets by a pappus is that of the raupo of our swamps and ponds. At the top of the flowering stem is a bare zone, where the pollen-bearing flowers, having done their work of shedding pollen, have withered away. Below is a compact cylinder of little nutlets arranged endon like cigars in a packet, but radiating from the central axis. bet us compare the arrangement with that of the dandelion head (A in diagram). There each nutlet is like a little umbrella, with the seedbearing portion for handle, a beak for shaft, and on the top a pappus of

radiating hairs for umbrella-spokes. The swollen seed-case is up against the plant, and the umbrella is open. Now in the raupo it is the tip of the umbrella which is the point of attachment to the central axis, and the seed ! is near the circumference of the cylinder. The umbrellas are all closed (for you can stand more closed than open umbrellas in a rack). So threadlike are the closed umbrellas that if you strip off. say, half an inch of the cylinder, and cause the umbrella ribs to open out by placing them to dry in the sun, your little thimbleful swells to a great fluffy heap. So far we have considered only the seeds that grow in dry seed-boxes, and are dispersed by wind or by slinging to animals. But in some cases the ovary wall, as it ripens to a seed-box, becomes soft, succulent, and attractive to animals. So we get stone-fruits and berries. The purpose of their succulence is to attract animals to eat the fruit, in the hope that the seeds will thereby be scattered,' the. stone or the seed-coats protecting the seeds from digestion, if they as well as the pulp are eaten. Now an interesting

point .is that the pulp of fruits contains little of the valuable protein food materials, as compared with the kernels (seeds) of nuts. The advantage to the plan is plain, when we recognise that what is spent in the fruit is lost, while what is stored in the seeds is legacy to the plant's children. It is said that, apart from the seeds, it requires 12 1 b of grapes, 21b of strawberries, 2!lb of appies, and 41b of pears to furnish as much protein ■as there is in one egg. (To be continued next Saturday.)