I86S i8$i] C. V. RILEY 385 



pressure, or to nitrogenous matter, but is exquisitively sensitive Letter 705 

 to the slightest touch. In our Drosera the filaments are not sen- 

 sitive to a slight touch, but are sensitive to prolonged pressure 

 from the smallest object of any nature ; they are also sensitive 

 to solid or fluid nitrogenous matter. Now in your Drosera 1 

 the filaments are not sensitive to a rough touch or to any 

 pressure from non-nitrogenous matter, but are sensitive to 

 solid or fluid nitrogenous matter. Is it not curious that there 

 should be such diversified sensitiveness in allied plants ? 



I received a very obliging letter from Mr. Morgan, but did 

 not see him, as I think he said he was going to start at once 

 for the Continent. I am sorry to hear rather a poor account 

 of Mrs. Gray, to whom my wife and I both beg to be very 

 kindly remembered. 



To C. V. Riley. 2 Letter 706 



Down, June 1st [1871]. 



I received some little time ago your report on noxious 

 insects, 3 and have now read the whole with the greatest 



Dioncea, nor have I met with anything more than general statements 

 about this plant or about Nepenthes catching insects." (From a letter to 

 Sir J. D. Hooker, July I2th, 1860.) 



1 Drosera filiformis : see Insectivorous Plants, p. 281. The above 

 account does not entirely agree with Darwin's published statement. The 

 filaments moved when bits of cork or cinder were placed on them ; they did 

 not, however, respond to repeated touches with a needle, thus behaving 

 differently from D. rotundifolia. It should be remembered that the last- 

 named species is somewhat variable in reacting to repeated touches. 



2 Charles Valentine Riley (1843-95) was born in England : at the age 

 of seventeen he ran away from home and settled in Illinois, where at first 

 he supported himself as a labourer ; but he soon took to science, and 

 his first contributions to Entomology appeared in 1863. He became 

 entomological editor of the Prairie Farmer (Chicago), and came 

 under the influence of B. D. Walsh. In 1868 Riley became State 

 Entomologist of Missouri, and in 1878 Entomologist to the U.S. 

 Department of Agriculture, a post he resigned in 1894 owing to ill- 

 health ; his death was the result of a bicycle accident. In Riley's 

 opinion his most important work was the series entitled Annual Report 

 oji the Noxious, Beneficial, and other Insects of the State of Missouri 

 (Jefferson City), beginning in 1869. These reports were greatly admired 

 by Mr. Darwin, and his copies of them, especially of Nos. 3 and 4, show 

 signs of careful reading. (Taken principally from the Proceedings of the 

 Entomological Society of Washington, Vol. III., 1893-6, p. 293.) 



3 Third Annual Report on the Noxious, Beneficial, and other Insects 

 VOL. II. 25 



