OEKETICO-rHYSIOLOGICAL STUDY ON THK FflRM.VTIoX ETi'. 59 



liiixliciiiicjil 111- physiological processes in tlio somatic cells that are set fi-ee 

 ]>y Hie con-cspoudiug gonetical make-up. 



In the case of the coloiir cluivacters in the awn of Oii/za mtiva, we are 

 api>:irently dealing with instances similar to those that were observed by Miss 

 WnKLD.OiE in Aidirrldnum and Bateson in Lcdlajrus. Suppose a pair of genes 

 C and c are concei-ned. The gane C produces the chrt)ü:ogeuic substance in 

 the bi-own awn to such an amount that it can readly lie detected in the 

 extract aiid by c, the production of the same substance is as much as ten to 

 twentj- times less tluiu that produced l>y C. Conseciuently the faint yellow 

 awn appears t<^) l>e devoid of chromogen. 



The oxidation and subsequent changes of the chromogenic suljstauce 

 leading to the formation of brown pigment may be due eutirel}- to jxjst moi-tem 

 chjinges and may have no relation to the action of a gene whatscever. If any 

 gene is concerned, we may suppose the following possibilities. 



Tlie gene C h;is the simidtiineous action of converting the chromogenic 

 substance to the brown ])igmout in which the oxidation plays an important 

 role. 



Ol- ^\■e may suppose that another gene 0, a chroraophelein, which con- 

 verts the chromogenic substance to the brown pigment, and the genes C and 

 are so linked each other that they may l)e considered as a single gene 

 complex. In the awn of Oryza, and in the seed coat of Glycine as we shall 

 see later, the chi'omogeuic substance and certain brown pigments which are 

 the oxidation product of the former, appear to be due to the action of a single 

 gene. Wherever the chromogenic substance is produced, it is invariably con- 

 verted to the pigment of phlobaphene natiu-e, unless the inhibitory gene enters 

 into the system. In this connection, it is of interest to refer the findings of 

 Wulff, Wolff and RorcHERMAXN' and Mrs. Wheld.\le Onslow (1919),'^ 

 who have shown in a number of cases that the reaction of direct oxidase is 

 invariably associated with the presence of the chromogenic substance. 



If the Litter assumption is adopted, the genes concerning the formation 

 of brown awn may be designated by CO and the £iiut yellow awn In- Co. 



1. WOLLF, .1., Loc. fit. 



■\VoLFF, J, and Eouchekmaxx, X. Loc. cit. 



2. Wheldale Onslow, JI., Oxidiziiig Enzymes. I. The nature of the " peroxidase " natur;»Uy 

 associated with certain direct oxidizing systems in plants. Bioch. .Jour. 13 : 1, 1919. 



