p. Keeble and E. F. Armstrong 283 



II. The Distribution of Oxydases^ in Plant Tissues. 



A. The Oxydases in the Vegetative Members of P. sinensis. 



The methods described in the previous section permit of the 

 mapping out of oxydases in the tissues of a plant with very considerable 

 accuracy. Hence it should be possible, by determining the distribution 

 of pigment and of oxydase in a given species, to obtain evidence as to 

 the validity of the hypothesis that the formation of anthocyan pigment 

 depends on the action of an oxydase on a chromogen. For. if oxydase 

 is specifically concerned in pigment formation a certain parallelism is 

 to be expected between the distributions of pigment and of oxydase. 



Before describing the results of our observations on the localisation 

 of oxydase in the tissues of Primula sinensis it is necessary to point out 

 that we must not expect to find an exact coincidence of pigment and 

 oxydase in each and every variety of this species. For, as shown by 

 Bateson, Gregory, and others, the range of pigmentation in both 

 vegetative and floral members of P. sinensis is very considerable. 

 Some varieties have white flowers and others have coloured flowers of 

 widely diflfering depths and shades ; some varieties possess green stems, 

 others reddish stems, and othei-s, again, deep red stems. 



Certain white-flowered, green-stemmed varieties, such for example 

 as Snow Drift (see Gregory, 1911) are lacking altogether in anthocyan 

 pigment. In other green-stemmed varieties the small amount of sap- 

 pigment which they contain is confined to special parts of the plant, 

 for example the roots, root-stocks, and bases of the petioles where it 

 occurs either in the epidermal cells only or in the sub-epidermal cells 

 as well. Of such minimally pigmented varieties, some possess no 

 pigment in their other vegetative parts, for example the flower- peduncle, 

 others, for instance. Sirdars, contain anthocyan pigment in isolated 

 epidermal and sub-epidermal cells of the flower-peduncle. 



Between the pure green-stemmed varieties and those with reddish 

 stems is a series of forms characterised by a progressively widening 

 distribution of epidermal pigment in the vegetative members ; and in 

 the reddish stemmed plants the pigmentation is wellnigh continuous 

 throughout the epidermal layer. At the other end of the colour series 

 are the dark red-stemmed varieties in which anthocyan pigment is 



^ For the sake of brevity we ase the term oxydase to connote both peroxydase and 

 oxydase and reserve for sub-section G (p. 304) the description of the distribution of these 

 bodies in the several tissues. 



