150 PLANT DISEASE 



other words, by manuring with nitrate, there 

 is a tendency to change the chemistry of the 

 insect in a way that is fatal to it by producing 

 more or less chlorophyll matter. 



Yet another insect to which the chemical 

 constituents that go to the making of chloro- 

 phyll appear to be noxious is the locust. 



That this view is not unreasonable is evident 

 from the remarks made on the subject in a 

 Micrographical Dictionary by J. W. Griffith, 

 M.D., and A. Henfrey, F.R.S., F.L.S., Pro- 

 fessor of Botany, in King's College, London, 

 under " Blood " 



" The blood of the invertebrata has not 

 been so thoroughly examined. In many of 

 them there are two circulating liquids one 

 coloured and sometimes containing haematine, 

 but no corpuscles ; the other colourless nucle- 

 ated corpuscles, much resembling the colour- 

 less corpuscles of the vertebrata. The colour- 

 ing matter of the aphides partakes of the 

 nature of chlorophyll." 



The locust is an invertebrate with a more 

 or less colourless circulating fluid. It is a 



