SCIENCE UP TO DATE.

Lyttelton Times, Volume CXIV, Issue 16326, 23 August 1913, Page 5

SCIENCE UP TO DATE.

MISCELLANEOUS REGENT ADVANCES. (By JAMES COLLIER.) , PLANT DISPERSION. 'The study of the geographical distribution of animals was hard until Darwin and Wallace applied to it their now conceptions of the origin of species, but it remained simple in comparison witb the far harder study of the geographical distribution of plants. The greatest Continental botanist of his day, Alphonse de Candollo, had virtually given it up in 1855, when its. advance had reached a deadlock. This was only three years before the reading of Wallace’s and Darwin’s fateful memoirs at a sessiou of the Linnean Socioty in 1858. And George Bentham, nephew of the famous Jeremy, as great a systematiser as his uncle was a codifier, intended to exhibit this “cul do sac” by reading at that same meeting a paper showing that in the fixity of species alone could bo found a solution of the problems of distribution. Yet at that very meeting the accepted doctrine of the fixity of species was for ever extinguished. Darwin’s general solution of the problem of distribution, says his son Francis, revolutionised the study. The assumption of the migration of species, together with their subsequent modification and the multiplication of new forms, answers all questions and overcomes all difficulties. Migration by itself would not suffice; modification by itself would not suffice; but the two united furnish a complete key. KRAKATOA. Few men havo made more (scientific) prophecies that have been fulfilled than Darwin. He had, indeed, none of the airs of the prophet, though the tall figure, when seen at an underground railway station in London, draped in a long, dark Highland cloak, suggested the idea of a modern prophet. But a conjecture of prevision of his, relating to the colonisation of islands, lias been amply realised on tho mountain slopes of Krakatoa. When tho eruption was completely at an end it was found that the vegetation that clothed its sides had been completely destroyed. It was buried under a long-glowing canopy of mud and stones. On the far-stretching South African pampas and the western plains of interior Australia the grass, after a drought, is to all appearance burnt to tho very root. Now let there be a moderate rainfall, and the grass springs up again as by enchantment. The roots had been alive all through the torrid glow of summer. Not so with Krakatoa. Yet another such miracle has been there performed. A German savant, Dr Ernst of Leipzig, informs us that the whole island is now being gradually clothed with verdure. We shall soon see there a green mantle of such luxurious vegetation as we expect to find in tropical latitudes. The annihilating ravages of a few days or weeks will be in time thoroughly repaired. REPARATIVE AGENCIES. . All of this new growth is not, like that of Australia or . the pampas, the revival of a dormant vegetation. It is tho upspring of an immigrant flora, brought up by tho - winds of heaven, the birds, and the marine currents. Seeds havo been carried from the adjacent islands or neighbouring continents. But not seeds alone. Trees bodily, or their trunks, or branches of them, bearing cones, the mothers of future forests, perhaps destined to be overwhelmed by future eruptions, are brought by tho sea-waves, and they may now bo*seen on tho beaches cr washed inland by tidal waves. On those floating pieces of wood have ridden ants, plants, lizards, even iguanas. Thus we perceive how Krakatoa and all other islands were originally colonised. We witness tho process of distribution of species, and as we. see the modifications they undergo, making of them new species, we may bo said to witness the. process of creation. For not all species that immigrate survive, but only the fittest, and in order to hold their own in the struggle for existence, these must adapt themselves to the new environment. The history of Krakatoa has still lessons to teach. BACTERIA AND THE SOIL.

At an earlier date than Dr Ernst’s researches the same volcanio island presented to the eye or the microscope of another German savant a very different spectacle. In 18S6, three or four years after the eruption, the late Dr Treub found it in such a condition as it may have exhibited in the immeasurably far-back ages when it was not yet a fitting home for tho plants and animals that were, in a later age, to become its denizens. It was still, as it had been immediately after the eruption, a mass of glowing ash; but, even so, its surface was already slimy with miscroscopic organisms, which are performing the task assigned them of breaking down the silicates of the rocks and forming soil. That the glowing ashes still retained some portion of their ancient fires made the island no purgatory to those micro-organisms. They revelled in the heat, as the blue-green algae live in the hot springs of Rotorua, Te Aroha and Hanmer Plains, and their sustenance was derived from the carbon, oxygen and hydrogen of the soil. When the chemists began their work on the constituents of tlio soil they saw in it nothing but chemical processes. Tho decomposition of plants in tho soil was a slow combustion. Then came Pasteur, who showed that the coil abounded in micro-organisms. He was followed, or accompanied, by Boussingault, who in 1859 asserted the existence of a microscopic vegetation under the outer surface of the earth. The chemists held their ground and it was not till 1879 that Schloesiug and Muentz proved that the processes governing the decomposition of the plants in tlio soil were vital still more than they were chemical. Warington confirmed the advance, and ilie organisms decomposing plant remains were isolated and their functions ascertained.

Hidden below the surface of the ground live countless myriads of microscopic or minute beings, which were found to bo totally different from those dwelling on its surface. They are of the most varied character, ranging from the most microscopic to large earthworms. In the first foot of the soil bacteria predominate. Their numbers almost transcend imagination; they have been counted with more or less exactness. As many as 31, 85, 40 and 50 millions have been reckoned to each gramme or grain of earth ,in I certain kinds of soil. The saturation point is attained only when 000 million bacteria dwell together in each centimetre of earth. Their numbers are very easily maintained. One bacterium divides into two at the end of thirty-five minutes. At the. end of twelve hours a single bacterium will have four million descendants. THEIR FUNCTION. Their primary task, at a time when there were no other living creatures on earth save themselves, was to break up the primitive rocks, whose silicates supplied them with sustenance. By so doing they created a basis for the higher plants that speedily (measured bv tho very long hand of the geological clock)’ began to grow there, and prepared the way for the animals that were to live on the plants. Then (it was boldly and brilliantly suggested in 1877 by a French philosopher) those primeval micro-organism turned ill fury, or with systematic ferocity, upon tho higher species that had supplanted them in the possession of the earth. Such was the original and fascinating idea of Alfred Espinas, and it has lately beer, confirmed by Professor Schwars. of Grahamstown, South Africa.

Such are the blue-green algoso that! Dr Treub found to cover the slopes of Krakatoa a few years after the eruption—thin, gelatinous layers that grew on tho volcanic ash and pumice. Such are those that Welwitz found on the black rocks of Angola, and Bohlin on the rocks of tho Azores. Sometimes they grow symbiotically—sharing a common life—with fungi, in order to form lichen, and are thus protected from desiccation. So act the blue-green algra in Angola, and the dried algw in tho interior of Australia form a. crust that resembles elastic bitumen. All of these species do more than cleave to tho rock surface. They eat and consume the rocks, as is proved by the corrosion of the rocks ana the contents of tho plant-cells. Thus a large part of their activities consists in breaking down the rock-surfaces. Carbonate of lime is secreted by a number of planLspecies—eoeeoliths and rliabdclitlis, blue-green algte and the red seaweed, and a number of lowly animals—all the protozoa and tho sponges. Countless plants and animals detach and secrete silica. Boring algte, fungi and sponges effect the destruction of oolite grains and shells. Bacteria feed on sulphur and separate it in two forms. The breaking down of tho insoluble element, phosphorus, anti making it soluble, is accomplished by bacteria. J Over somo of these processes and ovdr others, such as the decomposition of iron and sulphur, the chemists and tho biologists are still fighting a battle. Chemists maintain that these are purely chemical processes. A SECONDARY FUNCTION. The next great function of the microorganisms is the decomposition of tho residues of plant leaves, stems and organic matter generally. The effects °f this process on the soil are various. First, they are mechanical. They open up the soil and thus make room for water, increase the capacity of tho soil for holding it, and give a wider range for roots. Next, they are organic. They convert useless or harmless sbustances into food for plants. Those substances are resolved .into carbon dioxide, water, gaseous nitrogen (the most remarkable feature of the decomposition), ammonia and other mineral matter. EARTHWORMS. Somo thirty ears ago Darwin issued an attractive volume on the earthworm and its action on tho soil. It was to most readers nothing less than a revelation, and a large measure of truth cannot be denied to it. Over 50,000 worms inhabit a square acre of garden ground. They open up the ground and hew channels in it, where rain may penetrate and roots may find their wav. They, too, seem to act on stones and disengage their mineral elements. Finally and chiefly, they eat and ■ digest the leaves they drag down into their burrows, and give them back as worm-castings. Ten tons (so Darwin estimated) of material are thus treated by our 50,000 worms in the course of a year. . And thus they form the humus in which the higher plants grow.

We have seen that still tinier creatures than the common worm take an active part in preparing the soil for the uses of the higher animals and of man. Earthworms in part, no doubt, but perhaps still more the whole race of saprophytes, contribute to the pulverisation of tho rock and the formation of vegetal mould. The corpses of innumerable myriads of bacteria and fungi fertilise every foot of humus. We asked ourselves, when Darwin’s book was , published, why the systematic breeding of earthworms was not systematically pursued. We should now ask, why is not the fertilisation of the soil promoted, by the culture of bacteria and fungi? There is no need for the question. Hie thing is being methodically done. , .

EXPERIMENTS. A number of investigato'rs with high, scientific qualifications, possessing wellequipped laboratories, and ever experimenting on soils, since A. Koch set the example in 1899, havo in those few years achieved some noteworthy results. Samples of soil are inoculated' with solutions that favour one or another particular group of organisms. Tiiis particular group thrives while the rest are killed. A method that throws more light on the changes going on in the soil is partially to sterilise it by means of toluene or heat. Then the new flora thus favoured. is found to b 3 more active than the in-, digenous flora in decomposing certain organic matters, and an increase in the number of bacteria is found to in-_ crease the production of ammonia, which, again, enriches the soil. The effect of heat on the soil is found to be that it kills tho phagocytes that kill tho bacteria, übt it is inoperative on the bacteria. The type of flora thus produced is found to be superior to the old, and poisonous substances are removed from the soil. Such are a few of the more salient results of experimentation on the soil and its organisms. They are evidently tentative but they are yet considerable to be the outcome of a dozen years’ experiment. There is reason to believe that they will be far outdone Jiy the results of the second half of the first quarter of the new century.

GAVE ALL A FAIR TRIAL. “ For years I suffered from bron« chiti3 although I tried many patent medicines and doctors’ prescriptions, giving all a fair trial,” writes Mra Annie Lennon, Bridge Road, Drummoyne, N.S.W. “Then I tried Chamberlain’s Cough Remedy and from tha first dose got relief and kept on getting better. Sometimes in the winter I get a return of my old complaint, but in a very mild way, for Chamberlain’s Cough Remedy soon puts mo right.” 4