Plant oxydases and the chemical inter- 

 relationships of colour-varieties. 



By 



M Wheldale ''*^'^^'^'' 



m. wnemaie, NEW YORK 



Fellow of Newnham College, Cambridge. England. BOTANIC A I 

 QARDEN. 



As an outcome of the development of the science of genetics we 

 have come to look upon any species as a complex of unit characters. 

 In many cases these unit characters have been shown to be the 

 outward manifestation of the existence within the animal or plant 

 of definite bodies which have been termed Mendelian factors. The 

 inheritance and interrelationship of the factors for certain characters 

 are well known in many species, both of animals and plants, but of 

 the physiological nature of these factors we are almost entirely 

 ignorant. Yet, if the study of heredity is to occupy a central 

 position among the biological sciences, the necessity for identifying 

 Mendelian factors with the chemical or physiological constituents of 

 the animal or plant cannot be too strongl}^ emphasised. 



Thus, for instance, among the characters employed for working 

 out the problems of genetics, not one has proved more responsive 

 and fruitful of results than pigmentation. The knowledge, however, 

 that certain colours are due to the operation of certain Mendelian 

 factors is in itself insufficient. For, from the point of view of the 

 biochemist, a pigment is the product of certain metabolic activities; 

 these must be interpreted in terms of factors and for this purpose 

 both investigators must work hand in hand. 



With this end in view I have made an attempt in the following 

 pages to show how far the recent work of the biochemist upon colour 

 formation may be reconciled with the Mendelian conception of the 

 character pigmentation. 



Progressus rei botanicae III. 30 



