SOME MYSTERIES ABOUT PLANTS.

New Zealand Times, Volume XXVII, Issue 5665, 12 August 1905, Page 12

SOME MYSTERIES ABOUT PLANTS.

PLANTS THAT MUST HAVE FOOD IN ORDER TO LIVE. A SPECIES OF ACACIA GIVE BOARD AND LODGING TO CERTAIN ANTS IN RETURN FOR PROTECTION. THISTLES DISTRIBUTE THEIR SEEDS BY PARACHUTE. The latest development in plant culture is an extraordinary one. It is nothing loss than the inoculation of the soil. A very remarkable fact has long been known in connection with peas, beans, vetches, clovers, and other legumens. Though they have in their composition a comparatively large amount of nitrogen, they will grow well in soil which is practically destitute of it—which, too, is invariably found to contain more after they have been grown than it did before. Where and how do they get it? There is another peculiarity about these plants. Attached to the roots are shapeless nodules of various sizes. They were once supposed to be mere swellings or excrescences caused by disease, similar to the galls on certain trees. Some years ago, however, a famous French chemist discovered that they were due to the action of bacteria, and that these bacteria had the power to seize upon free nitrogen.in the atmosphere, and to convert 'it into compounds which could bo used by the plants as food. Here was the solution of what had hitherto been a most puzzling mystery. It showed why legumens arc independent of nitrogen in the soil, and how they are able to add it to the soil.

THE CULTIVATION OF BACTERIA

This discovery naturally suggested the idea that it might be passible to cultivate the bacteria, and by their moans to benefit the land and increase the amount of crops grown on it. In the investigations which followed, a German professor, Dr, Noble, took a leading part. After isolating the bacteria, he succeeded in cultivating them in an infusion of the plants with which they are found associated in nature. But the liquid, sold for a time under the name of “nitragen” proved a failure in practice. Dr. Nobies bacteria, when turned loose on the land, refused to do w'hat was expected of them. Dr. George Moore, an American scientist, who lias been experimenting with them, declares they were overfed. Provided with as much nitrogen as they required, he says, they lost the power to cater for themselves, and so became useless. He certainly seems to have proved his case. For with bacteria cultivated in a solution containing no nitrogen, lie has obtained some wonderful results—unfertile land rendered fertile, leguminous enormously increased in quantity, and a great improvement in subsequent crops in consequence of the improvement of the soil by the surplus nitrogen left in it.

HOW THE BACTERIA IS USED. Dr. Moore's solution may bo poured on cotton-wool, wiiich may then be dried and, strange as it may seem, keep almost indefinitely. In this state it may easily be sent any distance by post. When it is immersed in the same liquid as before, the bacteria revive and start on their work anew, multiplying with astonishing rapidity. This is "a fine obect-lesson, showing how disease germs may be carried from place to place in the clothes, and may lie dormant for months, if not for years, waiting only for favourable conditions to resume their baneful activity.

To use the bacteria, the solution containing them is either poured over the seeds, which in their turn may be dried preparatory to sowing, or else sprinkled over the soil. In either case the result is just the tame. Tho bacteria attach themselves to the roots of the plants arid proceed^to supply them with the nitrogen which is an e-'scntial part of their food. No doubt, when apparently working for others, they are really working for themselves. It may be regarded as certain that they receive some equivalent benefit in return, for sueh partnerships are never one-sided.

A PLANT AND ITS PARTNER.

An even more remarkable instance of

partnership between a plant and a different organism was discovered soma years ago in Nicaragua. In that country, and throughout Com tral America generally. It has beenfound almost impossible to grow English fruit trees, such as the apple and the pear, because of the ravages of the leaf-cutting ant, which utterly des troys the foliage. The native plants have been compelled to devise means of protecting themselves, the most curious being an alliance between a species of acacia and another ant, small in size, but exceed" ingly pugnacious, which attacks the leaf-cutter and drives it off. It exists in groat numbers, makes the acacia its permanent homo and forms its bodyguard. The inducements offered by the plant to its tiny ally are ample,, for they include board and lodging. It has developed hollow thorns in which the ants can live securely, and each leaf is furnished at the base with a gland which secretes honey, and at its tip with a small, sweet, pear-shaped nodule, which serves as food. What more could an ant want? This ant evidently thinks it has got a good thing, and is quite ready to fight for it. PLANTS WITH SOCIABLE HABITS. It is not merely with other organisms that plants associate for mutual, benefit ■ they also do so with one annolher. No" one who takes a country walk can help noticing that they gather together in groups, hero one kind and there another. Ibis is partly duo to tho fact that a position which suits one individual suits others of the same species, and as. they scatter their seeds around them a whole colony soon springs up where previously there was only a single settler. But there is more in it than that Tho taller and more striking kinds do not generally keep together in tills man-

But there is more in it than that The taller and more striking kinds do not generally keep together in this manner. Thistles for example, endeavour to get as far from one another as possible, and for this purpose each seed is suspended from a tiny parachute, which enables it to float a long distance on the wind.

Tlie plants with sociable habits are usually small, and bear inconspicuous flowers. If they grew singly they would run great risk of being passed unnoticed by the bees and moths, upon which they depend for their fertilisation, but when they are massed together it is different. Hence it is a very great advantage te them to live together in' colonies.