Nelson Evening Mail. SATURDAY, SEPT. 11, 1909. NATURE AT WORK.

Nelson Evening Mail, Volume XLIII, Issue XLIII, 11 September 1909, Page 2

Nelson Evening Mail. SATURDAY, SEPT. 11, 1909. NATURE AT WORK.

CLOTHING AN ISLAND. BEF*OKE the labyrinth of Nature" man's mind is amazed. The wonder, the beauty, tho farseeing character of it all strike him at tho outset, and at every turn now vistas of surpassing grandeur appoftr. . Not the least interesting is the manner in which Nature clothes with verdure a barren land cut off by miles and miles of sen from all growing .vegctaiou. The coral islands of the Pacific havo, up to the present, formod the most sinking examples of this quality of Nature; but some little time ago a volcanic eruption provided an excellent fiald for extensivo researches of this kind. In August, 1888, Karakatoa, a small island iu the Straits, of Sunda, midway between Java and Sumatra, was literally devastated by one 'of (ho greatest volcanic eruptions ou record. The whole surface . -was buried to an average depth of 98ft^ with pumice and ash. Tho island had been green with grasses, flowering plants, shrubs and trees. It was now a desert without a vestige of life, incapable of maintaining any jving thing, plant, or animal. But it was not long that the island remained in that state. To-day, a quarter of a century after tho utter destruction of organic life, it is again nestlod in green, and tho vegetation is said to be so dense in places that tho visitor lias to cut his way through. It is interesting to glance over - the observations which have been effected. Three scientific expeditions havo been made to the island since the erupcion, one in 1886,, a second in 1897, and the last in 1906 by Dr. Ernst, Professor of Botany in the University of Zurich. • •••.;•» It is necessary first of all to rocall to mind tho manner in which coral islauds are covered with verdure. The first germs of land plants are brought over by ocean currents, which^ carry seeds and tfruits to the -low-lying beach on tho emerging islands, It is only the so-called ''strand plants" that can be distributed in this way. As the islands rise and become covered with these plants, birds arrive. They, also, add to the variety of the island. A most interesting way birds carry seeds is by means of a natural hook which clings to their feathers. Ocoan currents and birds are the chie 1 agents in coilonising Coral islands with plants; but occasionally winds bring with thom spores and light seeds. It was Dr. Troub, director of tho Botanical Institute at Burtzeuyong, in Java, who led the two Karakatoa expeditions of 1886 and 1887, and he said ho fully expected to find the colonisation of that island brought about in the same way as that of coral islands; but as a matter of fact he found it has proceeded on quite different lines. From the scientific reports furnished it has been learnt that the vegetation did not spread from the beach to' the interior, nor has it had its beginning in sea drift. Tho stocking of the Btrand and slopes of the great volewnic cone beyond took place simultaneously; but in different ways, and with different plants. Iu the case of the strand it was the coral island vegetation over again; but in the puiuiee and ash, as well as on the exposed Tocks of the mountain ravines, the pioneers wero algae, diatomes, . and bacteria — all simple plant forms, evidently windborne to the island. Thoy covered the ash and pumice with a dark green, jolly-like coating, and formed a favourable soil for the spores of mosses and ferns aud such seeds of flowering, plants as are small enoutrli and light enough to be carried by air-currents. ■■ It was observed that, the air . brought flo'ra; of the interior rdoveldpccl much -'more Tapidly than" tho seabrought flora of the beach. The most remarkable feature of" ihe . rerStpeTySig wag the ?j)sed with which Nature, aa-. '■'."."■' ■'V'^'r •>"'"". ' ;-.r"' '''~Y. .''''"'' "" '..

idfliplished the work. Within three •ours, of tht? ertiptita th'evH t*rtS) Hi. 1 lido th'e &*iiufe? Slgae, diatoms and •acteria, quite a mass of ferns in Karakatoa. By 1897, fourteen ycr.rv ifter the eruption, vascular plants— -hat is, plants of high and more complicated structure than marely cellular—wore represented by 62 species, riiree ,vcafi* ago the vtwenlaf perils on the islitiid lifld riseu to 137 spec-ps, including representatives of every division of the vegetable kingdom. Anotlier interesting matter, which Kas boon revealed in connection with -••Ilie island, is the importnut part wli'icli bacteria play in the fertilisution oi the Bail*. Aftfe* th"6 oitlfttion the soil of Ki-akatoa contained no nitrogen, though it was well supplied Witl other ingredients required by plants Tho scientist explains that a certain amount of nitrogen from the atmps phero was, of course, oxidised, .-at elsewhero in the world under the in fluenco of electric discharges accom panying storms. This, eomittt*? fl*f)«» as nitrates Rli'd flitH'c acid in thi rain, together with the salts ani traces of organic matter in the vol canic ash, was enough to support .fo a year or so a rich flora of microsco pic -plauts whose germs wer brought by the winds. Tiles'-*, dt! caving under the operations o putrefactive bacteria, enriched th soil with nitrogen compounds. Ai enormous number of bacteria, whicl decompose celluloiso, starch, etc, wer among the. early plant colonists e Krakatoa. To it abo came the ui trate. bacteria, which work in the soi and convert amm&nia received fror the atmosphere during rain into ni trous and nitric acid. The acids ar then easily taken np by tho absort ing organs of vascular plants. Be sides these bacteria, a vast quantit; of nitrogen-fixing bacteria, which a. tually form the acids from atmo; pherie nitrogen, have been discovere on the island. One such a specie is stated to be new, and restricted a far as is yet known to the islani How it came to bo there is- no known; but scientists are much 'ii terosted as it suggests _ fasciriatin questions about the origin and mod fications of these early life-fonr Krakatoa constitutes the most con plete record of plant col&nis&tio j that is known,