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THE AMERICAN NATURALIST [Vol.XLIV 



The significance of the fact that I have succeeded in 

 producing 0. rubrineruis as one of the types resulting 

 from this cross, is too obvious to require pointing out. 

 In the light of these facts, it is not impossible that other 

 mutants can be similarly synthesized. 



Much experimental work has been directed to the study 

 of the physiology of anthocyanin production in the plant. 

 Without entering into the details of this work it may be 

 said that two general theories of anthocyanin production 

 have been developed. E. Overton ('99), Mirande ('07), 

 Molliard ('07) and others conclude that it arises from 

 an accumulation of sugars in the cell sap, which unite 

 with tannic acid to produce a glucoside. Overton showed 

 experimentally that low temperature and high light in- 

 tensity both cause anthocyan production. Mirande ( '(17) 

 called attention to the development of red in leaves eaten 

 by insects; 2 and Combes ('09a) produces the same result 

 by annular decortication. In every case the result is 

 interpreted as due to an accumulation of sugars. J. 

 Laborde ('08), from his experiments deduced a slightly 

 different view, namely that formaldehyde or one of its 

 polymerization products may cause tannin transforma- 

 tion, to produce color. Further, Overton, Laurent, 

 Molliard and others, found that various seed plants 

 grown in sugar solution show a marked increase in 

 anthocyan production, which indicated clearly a relation, 

 direct or indirect, between the presence of sugars and 

 the development of anthocyan. Whether such an in- 

 crease in anthocyan production is inherited is not known, 

 but presumably it would not be inherited. Of course, 

 many variations in pigment production are of a non- 

 heritable sort, but it is equally certain that in O. rubri- 



