5 I2 MISCELLANEOUS BOTANICAL LETTERS. [1873 



mersed in water they appear as if encased in thin glass ? It 

 is really a pretty sight to put a pod of the common pea, or a 

 raspberry into water. I find several leaves are thus pro- 

 tected on the under surface and not on the upper. 



" How can water injure the leaves if indeed this is at all 

 the case ? " 



On this latter point he wrote to Sir Thomas Farrer : 



"I am now become mad about drops of water injuring 

 leaves. Please ask Mr. Paine * whether he believes, from his 

 own experience ', that drops of water injure leaves or fruit in his 

 conservatories. It is said that the drops act as burning- 

 glasses ; if this is true, they would not be at all injurious on 

 cloudy days. As he is so acute a man, I should very much 

 like to hear his opinion. I remember when I grew hot-house 

 orchids I was cautioned not to wet their leaves; but I never 

 then thought on the subject. 



" I enjoyed my visit greatly with you, and I am very sure 

 that all England could not afford a kinder and pleasanter 

 host." 



Some years later he took up the subject again, and wrote 

 to Sir Joseph Hooker (May 25, 1877) : 



" I have been looking over my old notes about the 

 "bloom" on plants, and I think that the subject is well 

 worth pursuing, though I am very doubtful of any success. 

 Are you inclined to aid me on the mere chance of success, 

 for without your aid I could do hardly anything ? "] 



C. Darwin to Asa Gray. 



Down, June 4 [1877]. 



. . . I am now trying to make out the use or function of 

 "bloom," or the waxy secretion on the leaves and fruit of 

 plants, but am very doubtful whether I shall succeed. Can 

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

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



