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 (,;6,,ths inch), and for the 
“wet” 5 micromillimetres (s459th 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.1® 
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. 
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