150 



KNOWLEDGE 



1, 189C. 



total in Amsterdam and 

 and lycopods and half 

 in the Tristan d'Acunha 



Both are uninhabited. Sir George Stanton, a member of 

 Lord Macartney's embassy to China, was probably the first 

 Englishman who brought dried plants from these two 

 groups of islands. This was a century ago. l''or what is 

 known of the vegetation of the smaller islands of the 

 Tristan d'Acunha group we are wholly indebted to the 

 late Prof. Moseley, of the Clinllf)iii,r expedition. 



These islands support a much more luxuriant vege- 

 tation than those in higher latitudes to which I have 

 referred ; but here, as there, it is composed of few 

 species, thirty-eight bemg the 

 St. Paul Islands, half ferns 

 flowering plants, and fifty-five 

 group, whereof twenty-nine are flowering plants and 

 twenty-six ferns and lycopods. The composition of 

 the floras of those islands is exceedingly curious, for 

 although the majority of the endemic species belong to 

 genera that may be termed cosmopolitan, the bulk of the 

 vegetation of these two groups of islands, five thousand 

 miles apart, consists of Fkijlica nitida (Rhamnaceii'), a 

 shrub or small tree, and a reed-grass, S/iaitina arundinacca. 

 The latter is closely allied to a South American species, 

 but hitherto it has only been found in these islands. In 

 stature it is very different from our British species, which, 

 I may add, is a widely spread seaside plant, not only in 

 Europe, but recurring in North America and South Africa, 

 the nearest land to Tristan d'Acunha. Inaccessible and 

 Nightingale, the smaller uninhabited islands of the Tristan 

 group, are almost covered with Spartinu anmdinacea, 

 relieved here and there by clumps of the Plnjlicd. This 

 reed grows five to sis feet high, and in such dense masses 

 as to be impenetrable, except in the tracks made by 

 penguins, prodigiously numerous colonies of which it 

 shelters. It is equally abundant and luxuriant, in some 

 parts, at least, of Amsterdam Island. In St. Paul it 

 occurs in scattered clumps only. 



The genus PJu/lica is allied to the buckthorns, and is 

 represented in South Africa by upwards of thirty species ; 

 in the Island of St. Helena by one endemic species ; by one 

 or two in Madagascar ; and by P. nitida in Tristan d'Acunha 

 and Amsterdam I., which also inhabits the mountains of 

 Bourbon and Mauritius. It is the only woody plant in 

 the former islands bigger than the common crowberry, and 

 it forms woods m the main island of the Tristan d'Acunha 

 group and in Amsterdam, though it does not exist in the 

 fifty miles distant St. Paul. I have mentioned the crow- 

 berry (Eiiipetrum niijrutii) because this British shrub, 

 which is diffused all round the temperate and cold zones 

 of the northern hemisphere, is represented in the extreme 

 south of America, in the Falklands, and in Tristan 

 d'Acunha, and nowhere else in the world, by a 

 variety scarcely differing from the northern plant except 

 in having red instead of black berries. Several 

 other peculiarities in these remote insular floras offer 

 problems in the distribution of plants not easy of 

 solution ; but some remarks I have to make on this point 

 must be deferred. More than a third of the flowering 

 plants and ferns of the two groups of islands under con- 

 sideration are endemic. Of the remainder, some, especially 

 the ferns, are of wide range ; others are common to the 

 New Zealand and the South American regions, as well as 

 the intermediate islands whose vegetation I have already 

 described ; others, again, are partly common to the South 

 American region and the islands, partly to the New 

 Zealand region and the islands — Pelargonium australc, for 

 instance. 



The question how these and other remote islands 

 became more or less clothed with vegetation is a most 

 interesting one, and one that has been discussed and 



answered in a variety of ways. Few persons believe in a 

 special creation, but the existing vegetation may be the 

 remains of a former more extensive flora, and the islands 

 themselves remains of a former continent ; or it may have 

 been derived from other countries, conveyed by bii-ds, oceanic 

 currents, and other agencies, and the islands themselves 

 may be comparatively recent upheavals of the ocean bed. 



In KNowLKiKiK for December, 1805, is an illustrated 

 account of the appalling and disastrous eruption which 

 desolated the Island of Krakatoa and neighbouring countries 

 in 1H83. The island was torn and rent, and what was 

 left of it was covered with a layer of cinders and pumice 

 stone from one to sixty mitres in thickness, which was, 

 of course, at first of such intense heat as to utterly destroy 

 all animal and vegetable life. A spot of such absorbing 

 interest has naturally attracted the attention of all who 

 have passed within view of it, and it was actually visited by 

 a botanist (Dr. Treub) three years after the great eruption. 

 His observations teach us how an absolutely barren island 

 may become covered with vegetation. 



The island, as the destructive forces left it, is about 

 three miles across, and has an altitude of two thousand 

 five hundred feet. One side presents an almost perpen- 

 dicular wall to the sea, and the other side slopes steeply 

 to the shore. Its situation in the Sunda Straits is twenty 

 miles from Sumatra and twenty-one from Java ; and 

 the nearest point where there was terrestrial vegetation 

 is the Island of Sibesie, ten miles distant. When Dr. 

 Treub visited the island in 188C he found the elements of 

 a new flora, which he studied on the spot, afterwards 

 publishing the results in detail. 



The beginning of this new flora is the most instructive 

 phase to study. Cinders and pumice stone do not suggest 

 fertility ; but it is astonishing what moisture and chemical 

 action will do, and how one class of plants prepares the 

 matrix for others of higher organization. On this un- 

 promising medium the spores of filamentous alga; (chiefly 

 species of the universally dispersed genus J,ij7i;ihi/ii), carried 

 thither by the winds, were the first to germinate, causing 

 in their development a certain amount of disintegration. 

 Individually these organisms are microscopic, but they 

 multiply prodigiously, and form a green, film-like, gelatinous 

 tissue over the surface on which they grow. The action 

 of these organisms on the volcanic stratum, and their own 

 decay, formed a medium in which the spores of ferns, 

 brought by the currents of air, germinated and developed 

 into plants. In this early stage of the new vegetation of 

 Krakatoa, Dr. Treub observed eleven species of ferns, and 

 some of them were already common. In their turn the 

 ferns prepared the soil for plants of a still more complex 

 organization, namely, flowering plants belonging to various 

 families. At the time of Dr. Treub's visit plants of this 

 class were quite rare, though fifteen species had already 

 established themselves. These consisted partly of seaside 

 plants, whose seeds were undoubtedly floated to the island 

 and were cast ashore by the waves, and partly of plants 

 whose seeds were either dropped by birds or carried thither 

 by winds. Eight species were found on the moimtainous 

 interior of the island. Those on the seashore were all 

 plants that have a very wide range in similar situations in 

 the tropics, and are among those which first take posses- 

 sion of coral islands. The seeds of most of them have 

 been proved liy actual experiment to bear immersion or 

 " flotation " for a long period in salt water without losing 

 their vitality. Last year Dr. Treub visited Europe, and 

 on his homeward voyage passed within view of the island, 

 which, as he informed the writer, was then again covered 

 with vegetation. This is a most instructive lesson in the 

 natural distribution of plants, on account of its being the 



