Plant oxydases and the chemical interrelationships of colour-varieties. 467 



been destroyed by heat), of many plants, red or reddish brown pigments 

 were developed. These bodies can again be reduced to colourless 

 chromogens by the action of reducing agents. Hence Pal lad in 

 says there is, in general distribution among plants, a mechanism 

 consisting of aromatic bodies in combination with oxydases, for the 

 purpose of transferring atmospheric oxygen to bodies of a combustible 

 nature. Respiration, he maintains, is broadly separable into two 

 stages: first, the anaerobic splitting of carbohydrates into alcohol 

 and carbon dioxide and secondly, the aerobic oxidation of alcohol at 

 the expense of the "Atmungspigmente". P a 1 1 a d i n enumerates 

 anthocyanin among his respiratory^ pigments but he does not draw" 

 any distinction between the living product of oxidation and the 

 brown products of autolysis. 



Pigmentation and Genetics. 



Much light has been thrown upon the physiological nature of 

 pigmentation through Mendelian analysis. It is a matter of common 

 observation that natural species under cultivation give rise to 

 derivative colour-varieties, in some cases, to a very great extent. The 

 inheritance and interrelationships of the colour-varieties of several 

 species have now been worked out in detail and the main result of 

 careful analysis shows that for the production of the pigment of the 

 type, a large number of bodies, which may be represented as Mendelian 

 factors, are sometimes essential. Loss of some one or more of these 

 factors gives rise in turn to the horticultural varieties. If it be 

 granted that pigment formation is due to ferment action, then 

 the identification of some, at least, of the Mendelian factors for 

 pigmentation with oxidising enzymes is a reasonable inference. 



On this supposition, it is true, the development of anthocA^anin 

 becomes, in many cases, a highly complex process involving a series 

 of progressive stages. Yet a simple explanation would hardly be 

 adequate for the existence of some ten to twenty derivative varieties, 

 Mendelianly segregable and independently carrying the elements for 

 production of the colour of the type as proved by reversion on 

 crossing. 



If we select species having the most usual type colour, namely 

 bluish-red or purple anthocyanin. two main derivative classes are 

 commonly recognisable : 



1. The true red anthocyanic class. 



2. The non-anthocvanic or albino class. 



