Sunshine, Rain, and Wind 



This district consists of two quite different regions. 

 There is a dry, sunny, or wind-swept portion, and also 

 a sheltered or " wet " patana which is in the Hakgala 

 valley. These authors chose forty plants from the dry 

 and forty-two from the wet patanas, and after careful 

 microscopical measurements averaged the thicknesses 

 of the epidermis cell walls in these eighty-two cases. 

 They found that the average for the " dry " plants 

 was 6 micromillimetres (^{^ths inch), and for the 

 " wet " 5 micromillimetres (g^^th inch). This is a 

 good illustration, for the " wet " patanas have not really 

 a wet climate, as they are swept by westerly winds 

 during the south-west monsoon.^ 



The little sandwort, Sagina procumbens, has also been 

 examined in the same way. It was found that when it 

 grew on dry sand it had from three to four layers of 

 corky cells, but on moorlands only from two to three 

 layers. 18 



There are many other observations which might be 

 quoted here. Even in a garden one can find extraordi- 

 nary differences in the commonest weeds. 



A groundsel growing on a dry cinder path will have 

 a flat, often reddened rosette of short leaves, and one 

 small head of flowers nearly seated, or very shortly 

 stalked, in the middle of them. 



In dark places near some rank herbaceous plant, one 

 will find a tall, slender, drawn-out groundsel with two 

 or three nodding heads and long, distant leaves of quite a 

 different shape. It may even make a half-hearted at- 

 tempt to curve or twine round some strong branch. Such 

 a groundsel at once reminds one of the twiners common 

 in shady woods, whilst its ally on the cinder path is 

 like a very common type of the deserts and Tibet. 



Sunshine alone has extraordinary power to change 



* As regards other characters the authors have no very conclusive results. 



186 



