528 SCIENCE PROGRESS 



appear on the bare rock of Krakatau. Penzig later made further observations, 

 and now Ernst, especially by his bacteriological records, has gone far to present a 

 complete picture of the microscopic flora of the soil of the island. It is sufficient 

 to note here that the nitrite and nitrate bacteria and the nitrogen-fixing bacteria 

 were all found by him at Krakatau, and the leguminous plants, of which no less 

 than sixteen are present, all showed characteristic root nodules. 



The volume is thus of exceeding interest, as affording the most complete account 

 we possess of the colonisation of an isolated, originally entirely uninhabited 

 island, and also as being a very useful contribution to the question of the formation 

 of soil and the preparation of a medium capable of supporting the higher plants. 



W. G. Freeman. 



