May 6, 1909] 



NATURE 



279 



PLANT-LIFE IN KRAKATAU AND THE 

 MEXICAN DESERT.' 



ENGLISH readers owe a debt of gratitude to Prof. 

 Seward and the Cambridge Press for an English 

 edition of Prof. Ernst's account of the re-colonisation 

 of Krakatau. It is five-and-twenty years since Kra- 

 katau and the neighbouring islands in the Sunda 

 Strait between Java and Sumatra were transformed 

 by the most violent volcanic outburst of historic 

 times from forest-covered islands to deserts of pumice 

 and volcanic ash. Long regarded as an extinct vol- 

 cano, Krakatau, in the early summer of 1883, re- 

 sumed activity, and towards the end of August the 

 ■eruption culminated in an outbreak the effects of 

 which were felt over almost the whole of the earth's 

 surface. For a distance of twenty-two miles neigh- 

 bouring land was covered with glowing stones and 

 hot ashes, and it is estimated that the finer dust was 

 spread over an area of some 

 234,000 square miles. As a result 

 of this enormous loss of material, 

 a large portion of the island fell 

 in, and the Krakatau of to-day is 

 less than half the size of the island 

 of 1883, and has a quite different 

 outline. 



The islands therefore afforded 

 an unprecedented opportunity 

 for studying the development ab 

 initio of the organic popula- 

 tion of an oceanic island 

 , which rose several thousand 

 feet above sea-level. The nearest 

 land, the islands of Sebesi and 

 Sebpekoe, themselves half de- 

 ■btroj'ed by the effects of the erup- 

 :tion, is twelve to fifteen and a half 

 miles distant ; the nearest points of 

 Sumatra and Java are twenty-two 

 to twenty-eight miles distant. 

 Krakatau, the largest of the three 

 islands affected, consists of the 

 peak Rakata, 2700 feet high, 

 which, on the north side, towards 

 the disappeared portion of the 

 island, forms an almost vertical 

 wall, but on the south-east slopes 

 steeply to a fiat base in front of 

 which is a small, level beach. In 

 1886, when Dr. Treub visited the 

 island, its repopulation had already 

 begun. Blue-green algse, without 

 doubt wind-borne, had formed a 

 gelatinous layer on pumice and 

 volcanic ash, and on the exposed rocks in the 

 ravines on the mountain slopes ; these formed a 

 suitable nidus for the germination of wind-borne 

 spores of mosses and ferns, as well as of seeds. 

 Ferns preponderated at this early stage, being repre- 

 sented by eleven widely spread Indo-Malayan species ; 



lines as those of a coral island, where the elements 

 of the strand-flora, brought by sea, are of the first 

 importance. Here the wind-borne element played 

 the principal part, and the flora of the interior had 

 developed independently of the strand-flora, and with 

 much greater rapidity. 



It is to be regretted that more than ten years 

 elapsed before the sepond exploration of the new Kra- 

 katau in March 1897. The,, number of species was 

 then much increased, and .amounted to , fifty-three 

 seed-plants and twelve vascular cryptogams ; the 

 ground was, in some cases, completely covered, 

 and characteristic plant associations were .forming; 

 thus the Ipoinoea Pcs-caprae formation was a dom- 

 inant feature on the beach. Further inland the 

 vegetation constituted a kind of grass-steppe, the 

 grass occasionally reaching a man's height and some- 

 times forming a thick jungle. On the hills and 



earinE in the Strand-forest. To the left in the foreground Scaevola Koenigii ; behind the 

 , (SMchanim spantaiiciiui) a group of coco-nut palms. South-east coast of Krakatau. 

 ' The New Flora of the Volcanic Island of Krakatau." 



ridges were lower grasses with numerous ferns and 

 a few seed-plants; ferns still predominated largely on 

 the rock surfaces. Shrubs were few and trees rare. 

 Of the fifty-three seed-plants it was estimated that 

 thirty-two had come by sea, seventeen had been in- 



^ _ ^ __ ^ ^ __ troduced by wind agency, and four by fruit-eating 



rn""the drift-zone of'The beach* were se'edimgs o? ni^ne i animals or by man. The results of a third expedj- 

 phanerogams which had grown from sea-borne fruits \ t'O". >" 190S. have not been published In April 

 ' ^ ^ igo6, was planned the short expedition of which the 



present is an account. 



The progress made by the vegetation since 1897 

 was remarkable; almost the whole south side of the 

 island was seen to be covered with green. In the 

 drift-zone on the beach was a great variety of fruit 

 and seeds of land-plants, some quite fresh, some 

 alreadv germinated and rooted to the ground. They 

 represent the widely distributed strand-plants which 

 are the first colonists of recently formed coral reefs 

 and islands, and owe their buoyancy to air spaces 

 or light tissue in pericarp or seed-coat. Within the 



or seeds ; two of these were found in the interior and 

 on the mountain slopes, with the addition of {our 

 species of Compositse and two grasses, the fruits of 

 which had obviously been brought by air-currents. 

 Thus it was seen that the colonisation of an isolated 

 high volcanic island does not proceed on the same 



1 " The New Flora of the Volcanic Island of Krakatau." By Prof. A. 

 Ernst. Translated by Prof. A. C. Seward, F.R.S. Pp. vi-f 74; with two 

 sketch-roaps and 13 photographs. (Cambridge : University Press, igo8.) 



■' Camp-fires on Desert i 

 -with 72 illustrations (3 in c 

 .n.d.) Price i6j. net. 



)lour) and ; 



By W. T. Hornaday. Pp. 

 maps. (London : T. Werne 



NO. 2062, VOL. 80] 



