172 A NATURALIST IN THE GUI ANAS 



opposite to the Indian settlement on the left bank. The 

 roar of the water rushing between the masses of coal- 

 black rock, joined to the shouting of the men, tended to 

 make the scene an exciting one. Several times we landed 

 on the islands and walked along the banks while the boats 

 were being towed up. Some of these islands are simply 

 masses of bare rock, others resemble the lajas of the forest 

 and are covered with a similar vegetation. Fields of a 

 kind of wild pineapple occurred on many of the islands. 

 On this occasion the pineapples were green, but during 

 my first visit I tasted ripe fruit once or twice ; they were 

 so sour that I could never eat more than a small piece at 

 a time. The blocks of rock and stunted trees are in places 

 quite covered with festoons of the vanilla-vine. I never 

 saw this orchid in such abundance anywhere else. Any- 

 one living in the vicinity of the rapids who would take 

 the trouble to fertilise the flowers of the vanilla and pre- 

 pare the pods, would, I am certain, be able to obtain 

 hundreds of pounds of this valuable product during the 

 year. I explained this to Medina on my return to La 

 Prision, but although he appeared interested in all that I 

 told him concerning the vanilla, I do not expect that he 

 or anyone else at the settlement will take up the syste- 

 matic working of the wealth of vanilla at the rapids of 

 Mura and on the lajas of the forest. 



The river had fallen a good deal within the last few 

 days, so that many rocks that had been under water for 

 months were exposed. Some of these rocks were covered 

 with an aquatic plant which Isidor told me is much eaten 

 by tapirs. This plant (Neolacis corymhosa) was particu- 

 larly abundant in places where the current was strongest. 

 At first sight this neolacis, so soft and delicate, appears 

 out of place, growing as it does, exposed to the full force 



