Atkins — Oxydases and their Inhibitors in Plant Tissues. I4r5 



these all afforded dark-ooloured sap. The saps which were undarkened could 

 be divided into several classes as follows : — 



I. Those which contained oxydase, but were deficient in organic peroxide, 

 and accordingly only gave the guaiacum blue after the addition of hydrogen 

 peroxide, viz., the indirect reaction. This division includes — 



Wistaria .sinensis, leaves. 



„ „ petioles. 



Chamaerops hmnilis, leaves. 

 Cordyline australis, leaves. 

 Equisetum Telmateia, vegetative shoot. 



„ „ rhizome. 



Pteris aquiUna, very young leaves. 

 Eucalyptus globulus, petiole. 



Of the above, the leaf-saps were pale green, the Eucalyptus petiole light 

 red, and the Equisetum rhizome very liglit brown. 



On the border-line between those affording saps of dark and those 

 affording saps of light colour stands Sambiicus niger, which gave a light- 

 brown sap and direct guaiacum reaction when tested soon after pressing ; but 

 after standing in diffuse light for two hours it only gave the indirect reaction. 

 Addition of the fresh extract, boiled for two minutes, failed to bring about 

 the direct reaction ; accordingly it appears that the organic peroxide is 

 thermolabile. Fraximus excelsior also was found to give the direct action at 

 one time, the indirect at another. These facts are in accord with the con- 

 clusions of Keeble and Armstrong (15), who regard the presence of the natural 

 peroxide as variable. 



II. Plant tissues yielding a light sap, in which the presence of tannin 

 prevented the visible action of the oxydase : for example : — 



Equisetum Telmateia, spike or cone. 

 Eucalyptus globulus, leaf. 

 Ro&a rugosa, white petal. 



III. Tissues in which the absence of dark sap and of the oxydase reaction 

 in any form could not be ascribed to the inhibiting action of tannin, as in the 

 following : — 



Iris germanica, leaf. 

 Pteris aquilina, leaf. 

 Aspidium Filix-mas, leaf. 

 Being primarily concerned with cryoscopic determinations of osmotic 



X 2 



