596 



A NATURALIST IN THE PACIFIC 



it is 95° to ioo°. Salt-marshes situated behind a beach even in a desert- 

 region change its thermal behaviour, and it would then be more like a beach 

 skirting a vegetated sea-border in the same latitude. The method of 

 observation was as follows : — An unmounted thermometer of the size of a 

 clinical thermometer, but graduated higher, was placed horizontally in the 

 sand half an inch below the surface and a reading taken. It was then 

 pushed vertically into the sand until the bulb was four inches deep and 

 another reading taken. Provided that the sand is moist beneath, the 

 colour does not seem to make much difference, except perhaps in very 

 dark sands, none of which were tested. 



Ordinary Beach-Temperatures with an Unclouded Sky in the Hot Season 

 during the Early Afternoon. 



This illustrates only the average condition. On a calm day in the case of a beach 

 facing south in the South of England, I have obtained exactly the same readings in July 

 as at Valparaiso in January, 112° at surface, 80° four inches deep. 



NOTE 71 (page 479) 



On the Buoyancy of the Seeds or Seed-vessels of some Chilian 



Shore Plants 



(i) Nolana, probably paradoxa. Common on the beaches of Southern 

 Chile. The ripe drupes have a somewhat fleshy outer covering which they 

 lose when lying on the sand, and present themselves then as dark-brown 

 angular " stones," often five to six millimetres across. Inside the outer 

 hard covering of the stone is a layer of spongy tissue which gives 

 it buoyancy ; but since these coverings are wanting at the scars marking 

 the basal insertion of the drupe, the embryo seems insufficiently protected 

 against injury during flotation in sea-water ; and the seed-vessel at first 

 appears to be only fitted for conveyance by the currents over a limited 

 tract of sea. However, in a preliminary experiment on seed-vessels that 

 had been kept a few weeks, I found that 30 per cent, floated after three 

 weeks in sea-water. Subsequently, after drying for a year, the seed-vessels 

 were again tested in sea-water, nearly all of them floating after three 

 months' immersion. Two of them, removed after six weeks' flotation, 

 germinated healthily. These fruits are common in beach-drift between 

 Corral and Valparaiso. 



(2) Raphanus, near R. maritimus. Growing near beaches in South 



