102 THE VALUE OF COLOUE 



of concealing themselves either to avoid danger, 

 or to spring upon their prey.'^ 



Protective Kesemblance of a very marked 

 and beautiful kind is found in certain plants 

 inhabiting desert areas. Examples observed by 

 Burchell almost exactly a hundred years ago 

 have already been mentioned on pp. 96-8. In 

 addition to the resemblance to stones Burchell 

 observed, although he did not pubHsh the fact, 

 a South African plant concealed by its likeness to 

 the dung of birds.^ The observation is recorded 

 in one of the manuscript journals kept by the 

 great explorer during his journey. I owe the 

 opportunity of studying it to the kindness of 

 Mr. Francis A. Burchell of the Ehodes University 

 College, Grahamstown. The following account is 

 given under the date July 5, 1812, when Burchell 

 was at the Makkwdrin Eiver, about half-way 

 between the Kuruman Kiver and Litakun the old 

 capital of the Bachapins (Bechuanas) : — 



' I found a curious little Crassula (not in flower) so snow 

 white, that I should never has [have] distinguished it from 

 the white limestones. ... It was an inch high and a little 



' Zoonomia, i. London, 1794, 509. 



* Sir William Thiselton-Dyer has suggested the same method of 

 concealment (^«Mafe o/ Botowy, XX. 123). Referring to Anacamp- 

 seros papyracea, figured on plate ix., the author says of its adaptive 

 resemblance : ' At the risk of suggesting one perhaps somewhat 

 far-fetched, 1 must confess that the aspect of the plant always 

 calls to my mind the dejecta of some bird, and the more so owing 

 to the whitening of the branches towards the tijps' (ibid., 126). 

 The student of insects, who is so familiar with this very form of 

 protective resemblance in larvae, and even perfect insects, will not 

 be inclined to consider the suggestion far-fetched. 



