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THE AMEBIC AN NATURALIST [Vol. XLIII 



The Reestablishment of the Flora ox Kbakatatj 

 AVlien the island was first visited by a geological ex- 

 pedition two months after the eruption, the whole surface 

 was buried under a layer of ashes and pumice averaging 

 thirty meters in depth, and in some places as much as 

 sixty meters. Thus, of course, every trace of life must 

 have been quite annihilated and the sterilization was com- 

 plete. An analysis of the ashes showed that, except for 

 phosphorus and nitrogen, all of the elements necessary 

 for plant life were present. (See Ernst, p. 50.) Ernst 

 suggests that the other elements necessary for the estab- 

 lisliment of a new flora were conveyed from the main- 

 land in the form of dust, and that as a result of the in- 

 tense electrical activity which accompanies the almost 

 daily rains of the equatorial region, the atmospheric 

 nitrogen is oxidized into the nitric and nitrous acids 

 which furnish the necessary nitrogen. This with the 

 salts and traces of organic matter in the ashes would 

 have been sufficient in a very short time to allow the es- 

 tablishment of the first micro-organisms upon the island. 



The first botanical expedition, as already stated, was 

 made under the direction of Professor Treub in 1886, 

 three years after the eruption. During this interval a 

 considerable number of plants had already established 

 themselves upon the island. The most important fact 

 brought out by this trip was the great importance of the 

 blue-green alga? in the early establishment of the new 

 vegetation. Thin blackish, slimy films, formed by a 

 number of species of Oscillatoria and other blue-green 

 forms, were found in great quantity coating the surface 

 of the ashes, and the gelatinous matrix of these low plants 

 offered a substratum which was favorable for the germi- 

 nation of the spores of ferns and even for the seeds of 

 a few phanerogams. It was found that the colonization 

 of the island was quite as marked in the interior and 

 upon the high cone as it was along the shore, but the 

 plants of the interior of the island were for the most part 



