F. Keeblb and E. F. Armstrong 309 



P. sinensis the surface of one of which was wounded in several places by 

 means of the point of a needle. The flowers were transferred at once to 

 the benzidine reagent and treated subsequently with hydrogen peroxide 

 with the result that the wounded areas gave an intense peroxydase 

 reaction. It is therefore evident that the wound oxydase is in this 

 ease of the nature of peroxydase. Experiments of a similar nature 

 made with other flowers lead to the conclusion that when a peroxydase 

 only is present in the coloured or white parts of the petals the effect of 

 wounding is to bring about copious liberation of peroxydase, but when a 

 direct oxydase is present wounding results in the liberation of direct 

 oxydase. 



The main ftxcts dealt with in the foregoing section may be sum- 

 marised as follows : 



Cells in which anthocyan pigment is present contain oxydase in one 

 of two forms, namely peroxydase or complete (direct) oxydase. The 

 latter is found in the Howers of Sweet William {Dianthus barbatus), of 

 Geranium sanguineum and certain species of Pyrus and Prunus. The 

 former, of more general distribution, occurs in P. sinensis, Lathyrus 

 odoratus, Pisuni sativum and many other plants. 



The oxydase content of a plant varies with external conditions. A 

 tissue of a normally illuminated plant contains less peroxydase than is 

 contained in the corresponding tissue of a plant kept in darkness ; and 

 the organic peroxide constituent of the complete oxydase, though it 

 may be absent from the normal plant, makes its appearance after that 

 plant has been maintained for some time in darkness. 



The wound oxydases of plants resemble those which are concerned 

 in the work of pigment production. Those plants which contain per- 

 oxydase only, liberate, when lacerated, wound peroxydase and those 

 which contain both peroxydase and organic peroxide show in their 

 wounds the complete oxydase. 



For summaries of other subsections see pages 288 and 303. 



In conclusion we wish to express our thanks to Miss D. Richardson 

 for her kindness in preparing the coloured drawings from which the 

 figures of Plate XIX are reproduced ; to Messrs Sutton and Son and to 

 Mr Macdonald, the Primula expert of that firm, for providing us with 

 some of the material used in the course of the experiments, and to 

 Mr G. Coombs, Assistant Lecturer in Botany, University College, 

 Reading, for the drawings represented in Text-figures 1, 2 and 3. 



