F. Keeblb and E. F. Armstrong 289 



B. The Oxydases of the Flower of P. sinensis. 



(1) Self-Coloured Varieties. 



The oxydases of the vegetative parts of Primula sinensis are located 

 in two groups of tissues ; one group — the epidermal — ^is superficial, the 

 other — the stelar — is deep seated. The "epidermal" oxydase is con- 

 fined to the epidermis in certain green-stemmed varieties but extends 

 to the sub-epidermal layer in reddish-stemmed varieties and reaches its 

 widest distribution in the dark red-stemmed races in the peduncles of 

 which oxydase occurs not only in the epidermis but also in the two or 

 three outer layers of the cortex. Hence it follows that the epidermal 

 oxydase is separated widely by the intervening cortical cells from the 

 bundle oxydase. 



The epidermal and bundle oxydases of the vegetative members have 

 their counterparts in the flower ; but, inasmuch as the cortical tissues 

 of the corolla consist only of some two layers of flattish cells, the 

 epidermal and bundle oxydases of the petals lie in close proximity with 

 one another. Nevertheless, and in spite of their proximity, it is possible 

 to demonstrate macroscopically the presence of both oxydases in the 

 petals. The discrimination between the two oxydases is aided by the 

 fact that they do not react in precisely the same way to our reagents — 

 a-naphthol and benzidine. The former reacts much more quickly and 

 in most cases exclusively with the bundle oxydase to produce a lavender 

 blue colour which picks out the veins in exquisite detail and for the most 

 part leaves the epidermal oxydase unaffected. The selective action of 

 benzidine is less precise. This reagent reacts with the epidermal oxydase 

 to produce a rich brown colouration of the superficial layer of the petals 

 and also produces a similar though darker colouration in the veins. 



Examples of the colour reactions which are obtained by the use of 

 these reagents are given in Figs. 2, 4, 5, 11, 12, 14, Plate XIX. 



The coloured (blue) flower shown in Fig. 1 yields with benzidine 

 the reaction illustrated in Fig. 2. Recessive whites give a precisely 

 similar reaction (see Fig. 5) with this reagent. Unlike benzidine, 

 which reacts with epidermal and bundle oxydase, o-naphthol reacts 

 with the latter only both in the case of coloured and of recessive white 

 flowers. Hence as shown in Fig. 4 the veins stand out prominently on 

 an almost unstained ground. 



The central part of the corolla of these varieties is characterised, as are 

 many other varieties of P. sinensis, by a yellow eye, the colour of which 



