512 Armstrong . — The Function of Hormones in 
determine the liberation of hydrogen cyanide from the cherry laurel, the 
leaf of this shrub changes in colour from green, not merely to brown but to 
a rich chocolate brown-black and ultimately to black. On this account, as 
it carries its own indicator, it may be used even more effectively than the 
laurel leaf and with less trouble ; otherwise its behaviour is precisely similar 
to that of the laurel leaf. 
It has been shown by Bourquelot and Herissey 1 that all the organs 
of Aucuba , the seed kernel especially, contain a crystalline glucoside, aucubin, 
Ci 3 H 19 0 8 , which is resolved by ‘ emulsin ’ into glucose and aucubigenin, 
C 7 H 9 0 3 (?). This latter, however, is so unstable a compound that it has not 
been isolated ; as it is liberated it undergoes decomposition spontaneously 
into a black substance that is insoluble in water, alcohol, ether and even in 
a solution of caustic soda. According to Bourquelot and Herissey, the 
change takes place in absence of oxygen ; Maquenne and Demoussy, 2 who 
have used Aucuba together with other leaves in studying the effect of ultra- 
violet light in comparison with that of heat and chloroform, have arrived at 
a similar conclusion. 
Maquenne and Demoussy have stated that if the leaf be kept in boiling 
water sufficiently long to destroy the enzyme, it nevertheless blackens sub- 
sequently ; they have attributed the change to the slow hydrolysis of the 
glucoside under the influence of acid present in the leaf. We have not 
observed this effect when the leaf has been kept sufficiently long in boiling 
water ; neither the leaf nor the aqueous extract in contact with it has 
changed in colour, although this latter has blackened rapidly after emulsin 
has been added to it. 
Several varieties of Aucuba Japonica are in cultivation — most of these, 
especially the longifolia variety, behave precisely like the common form ; 
but one (A. Japonica , var. vera) which we owe to the courtesy of Mr. L. R. 
Russell, of Richmond, does not blacken to any appreciable extent. Berries 
of this variety obtained by fertilizing with pollen from the male of the common 
form evidently contain much aucubin, as they blacken quite readily ; it is 
not improbable, therefore, that Aucuba may furnish an interesting subject 
of study from a Mendelian standpoint and we hope to carry out experi- 
ments from this point of view. 
Aucubin has been separated from a number of varieties of Aucuba by 
C. Lebas. 3 
The only other shrub we have met with that is at all comparable in its 
behaviour with Aucuba Japonica is Azara microphylla ; the leaves of this 
shrub become a rich brown when exposed in chloroform vapour. We have 
not succeeded in obtaining from this an extract which changes colour when 
1 Ann. Chim. Phys., 8 me ser., t. iv, pp. 289-318. 
2 Comptes rend., t. cxlix, 1909, p. 957. 
3 Journ. Pharm. Chim., t. xxx, 1909, p. 385. 
