168 A NATURALIST ON THE "CHALLENGER." 



projecting rock-masses already mentioned, but are dwarfed and 

 almost hidden amongst the mosses. They grow in greatest 

 luxuriance on the damp banks of the stream. 



The mosses are in most striking abundance,* and, in some 

 very wet places, form continuous sheets over the ground many 

 square yards in extent. Lichens are not in very great quantity, 

 except the incrusting forms, which are tolerably abundant 

 on the rocks. 



An attempt was made to reach the actual upper limit of 

 vegetation, but failed from being commenced too late in the day. 

 The ascent was up the bed of the small stream already men- 

 tioned, which lay at the verge of one of the modern lava-flows, 

 where it abutted on a low cliff exposing a more ancient flow in 

 section. The more recent flow had a very gradual inclination of 

 not more than 8°. The first scattered patches of snow were 

 encountered at about an elevation of 800 feet. A patch of the 

 cabbage was met with at 1,000 feet. 



The highest point reached was at about 1,500 feet elevation. 

 Here Ranunculus biternatus had disappeared, and where growing 

 a little lower down was very much dwarfed. The Azorella, 

 with a few mosses, formed the principal vegetation; but the 

 green was merely dotted over the bare rock and stones. The 

 patches of snow were here frequent. The Azorella appeared 

 from this point to be continued on for about 300 feet more, 

 becoming scantier and scantier. The absolute limit of vege- 

 tation may probably be placed at about 2,000 feet. The part 

 explored was somewhat sheltered. A red cone of scoria? more 

 exposed was quite bare of green from about 1,000 feet elevation 

 upwards. 



At about 1,400 feet elevation, the water in a shallow pool 

 exposed to the sun was found to have a temperature of 65° F., 

 the temperature of the air in the shade being 44°. At 900 feet 

 a similar pool, but one which had a small stream of colder water 

 running into it from the cliff, had a temperature of 55°, the air 

 here being at 45°. The thermometer here, when plunged into 

 the midst of a rounded mass of Azorella, rose to 50°. It is 



* Thirty -one species were collected, five of which are described by 

 Mr. Mitten as new. 



