THE SEED ITSELF.

Otago Witness, Issue 3030, 10 April 1912, Page 14

THE SEED ITSELF.

A knowledge of the seed which is sown by every farmer would enable him to determine several tilings about his work which would help to make it more successful. Such a knowledge would throw some light on such points as the quantity to sow, the necessity for a perfect seedbed, the chances of thick or thin sowing, and tlie necessity for having abundant plant food available at all stages of its growth. The constituents of the seed. besides the embryo, are: (]) Starch (in cereals, legumes, etc.), contained in the cotyledons or seed lobes ; and (2) fat (in certain seeds and nuts). The requisite conditions for germination to take place are the presence of moisture, atmospheric oxygen, and a suitable temperature. By means of these, various chemical changes occur in the starch and fat whereby the embryo is nourished and grows; while the chief ingredients in the ashes of seeds are potash and phosphoric acid. These points may be shortly discussed. The seed of all grain possesses (l'l a coat of one or more membranes, which, on germination, is buret and thrown off; (2) an embryo, where is situated the seat of life ; and (3) a store of food for the nutrition of the embryo until it has developed sufficiently to live on the soil and the air. A sufficient degree of moisture is necesary to get at the embryo under the thick coat of the seed ; hence the ground requires to be fine and retentive of moisture to set up the initial process. For each species there is a minimum temperature of the ground below which no germination will take place, and also a maximum one which prevents it from doing so. And approaching

each of these extremes the germination is so slow and irregular that- the young growth is liable to perish while in such a critical condition. The practical conclusion is that it is no use to sow until the season is warm enough to ensure sufficient warmth in the ground. Therefore that dead portion of the year from the middle of June till the middle of Julyshould be avoided for grain-seeding in the south. That time cannot in an ordinary season be utilised for wheat without considerable risk. The next indispensable factor is the presence of air. The oxygen of the air is the chief material absorbed by the seed during germination. Some of the charcoal or carbon in the food reserve begins to bran with the assistance of the oxygen, which the seed absorbs from the air. Warmth and_ the giving off of charcoal fumes or carbonic acid, the breath of the plant, are the outward results, while the food of the seedling is made liquid and ready for immediate use. Again the practical lesson is clear, the ground must be in fine division, loose, and free at seedtime to admit the air, and what is equally important, allow the deadly carbonic acid gas to escape. Since the* food stored up in the seed will give out in a stated time, the condition of the ground must be such that the fine rootlets may build up a plant ca|iable of carrying on an independent existence. The larger and fuller the seed the more reserve of food is there and the longer the young plant can grow from the seed store alone. For the reasons given the depth at which seeds can be sown is determined by their size.