TRANSACTIONS OF SECTION B. 439 
4. Report of the Committee on Plant Enzymes.—See Reports, p. 115. 
5. The Distribution of Orydases in White Flowers. 
By W. Newson Jonss, M.A. 
In a recent communication to the Royal Society (Keeble and Armstrong) it 
has been shown that oxydases and peroxydases occur in the petals of flowers and 
elsewhere; and that their presence and distribution can be demonstrated by the 
use of benzidene and a-naphthol. Colour is produced by the action of these 
oxydases and peroxydases on a chromogen—i.e., a colourless body which 
becomes coloured on oxidation. 
In white flowers absence of colour is presumed to be due to the absence of 
one or both these bodies, or to the presence of an inhibitor checking the action of 
the oxydase or peroxydase. 
The present investigation was undertaken in order to obtain further evidence 
as to the conditions which determine the absence of colour in white flowers. 
The evidence obtained points to the occurrence of the following types of 
white flowers :— 
(a2) Those in which a chromogen and an oxydase both occur, but only react 
together after treatment with chloroform, ether, alcohol, &c. This may be 
due to the localisation of chromogen and oxydase in different cells of the tissue, 
but still requires histological confirmation. (Cf. Guignard.) 
(8) Those containing chromogen and geroxydase with, presumably, a similar 
distribution, and requiring the addition of H,O, to produce a reaction. 
(y) Those containing a peroxydase, but no chromogen body with which it can 
react. Such petals give a reaction with benzidene and H,0,. 
Types possessing (5) an oxydase but no chromogen, and (e) a chromogen 
without oxydase or peroxydase, have not yet been met with. 
A chromogen has been extracted from type (a) (after destruction of the 
oxydase by boiling) which can be used to demonstrate the distribution of 
peroxydase in, e.g., petals of type (y) in the same way as benzidene. 
The term chromogen as used above is applied to a colourless body which 
becomes coloured when acted upon by an oxydase or peroxydase. It is fully 
realised that this extracted chromogen may not be identical with that responsible 
for the colour in the flower of coloured varieties of the same species. 
6. The Blackening of the Leaves of Aucuba japonica. 
By Sypney G. Patns, B.Sc., F.I.C. 
The blackening of leaves of Aucuba japonica is due to the formation of a black 
pigment by oxidation of aucubeginin, which itself is a product of the splitting of 
the glucoside aucubin. The blackening of the leaves under the influence of 
anesthetics such as chloroform, toluene, alcohol, &c., was first shown by Guignard 
and Mirande, and it has been clearly proved by Maquenne and Demoussy to be 
due to the action of enzymes. 
These anesthetic substances have been grouped together by H. E. and E. F. 
Armstrong as a class of Hormones, these workers apparently using the term 
hormone to signify any substance capable of activating an enzyme. 
Blackening of the leaves can, however, be brought about under conditions 
wherein the possibility of intervention of any such activating substance would 
seem to be very remote. 
For example, leaves are blackened :— 
1. When heated to a temperature approximating to 60° C. 
At 5(°C. blackening commenced after 46 min. 
” 5. S C. ” ” 28 ” 
ayn. a <3 6 ,, and was complete in 21 min. 
” 55° : ” ” 4 39 ” 9 7 9? 
, 51°C. ” 9 3 9 3? ” + ” 
2. When submitted to a temperature below — 7° C. 
3. When dried in air. 
4. When partially dried in an atmosphere with vapour tension less than that 
of the cell sap. 
