1 877.] BOTANICAL LETTERS. 341 



you give me any light ? Are such plants commoner in warm 

 than in colder climates ? I ask because I often walk out in 

 heavy rain, and the leaves of very few wild dicotyledons can 

 be here seen with drops of water rolling off them like quick- 

 silver. Whereas in my flower garden, greenhouse, and hot- 

 houses there are several. Again, are bloom-protected plants 

 common on your dry western plains ? Hooker thinks that they 

 are common at the Cape of Good Hope. It is a puzzle to me 

 if they are common under very dry climates, and I find bloom 

 very common on the Acacias and Eucalypti of Australia. 

 Some of the Eucalypti which do not appear to be covered with 

 bloom have the epidermis protected by a layer of some 

 substance which is dissolved in boiling alcohol. Are there 

 any bloom-protected leaves or fruit in the Arctic regions ? 

 If you can illuminate me, as you so often have done, pray do 

 so ; but otherwise do not bother yourself by answering. 



Yours affectionately, 



C. Darwin. 



C. Darwin to W. Thiselton Dyer. 



Down, September 5 [1877]. 



My DEAR Dyer, — One word to thank you. I declare had 

 it not been for your kindness, we should have broken down. 

 As it is we have made out clearly that with some plants (chiefly 

 succulent) the bloom checks evaporation — with some certainly 

 prevents attacks of insects ; with some sea-shore plants 

 prevents injury from salt-water, and, I believe, with a few 

 prevents injury from pure water resting on the leaves. This 

 latter is as yet the most doubtful and the most interesting 

 point in relation to the movements of plants. 



