Fortunate Islands 



seeds must reach it, but they must also be able to grow 

 upon its special soil. 



When Dr. Schimper visited a lava-flow (eruption of 

 1843) in Western Java, he found that there were no trees 

 upon it.^ The surface had been no doubt inhabited first 

 by the blue-green algae (p. 20), and then by ferns which 

 were still numerous enough. But though the rich 

 tropical forest was in full vigorous development beyond 

 the lavas, the only plants which had managed to settle 

 upon its surface were orchids and other Epiphytes such 

 as occurred elsewhere on the branches of the forest-trees, 

 as well as a peculiar rhododendron, an insect-devouring 

 Nepenthes, and others which belonged to dry or rocky 

 habitats. 



All of them were adapted to obtain their nitrates and 

 other food not so much from the soil as from the atmos- 

 phere or from peaty material. 



Mr. Ridley has shown that when a bare tree branch 

 in a tropical jungle is colonised by Epiphytes, the process 

 is not unlike that which happened on Krakatoa. First 

 blue algae establish themselves, then it is overgrown 

 by mosses and ferns, and then the orchids and other 

 flowering plants plant themselves upon it.^ 



The seeds of these orchids are exceedingly minute, 

 and remind one of the dust-like spores of algae, mosses, 

 and ferns ; they are easily blown by the wind or 

 carried by birds from branch to branch, or to desolate 

 lava-flows, and even to lonely islands far out to sea. The 

 stalks of these orchids generally hang down, or droop 

 over the branches, so that the flowers are quite con- 

 spicuous, but when in fruit the stalk is erect, so that the 

 tiny seeds are shaken out of the capsules by any violent 

 wind. 



On these lonely islands of the Pacific, then, one would 

 expect a large percentage of the plants to possess small 



277 



