The Localization of the Indigo-producing Substance 
in Indigo-yielding Plants. 
BY 
H. M. LEAKE, M.A., F.L.S. 
With Plate XIII. 
T HAT there is present in numerous plants scattered through the 
vegetable kingdom a body which, under certain conditions, is capable 
of yielding indigo has been a matter of general knowledge from very 
remote ages. This knowledge, however, was chiefly acquired as the result 
of the utilitarian purposes to which indigo is put ; thus the woad, Isatis 
tinctoria , L., was largely cultivated in Europe until the dye so obtained was 
replaced by indigo imported from the East ; Polygonum tine tor inm , Ait., 
was, and is still, cultivated in China ; Indigofer a argentea , L., is the ancient 
* nil 5 known to, and cultivated by, the Egyptians ; and there are cultivated, 
chiefly in India and Java, other species of Indigofer a too numerous to be 
mentioned individually. 
Literature. 
Schunck in 1855 ( 1 ) attempted to obtain some knowledge of the body 
which existed in the woad and from which indigo could be obtained. To 
this body he gave the name c Indican.’ 
During the last twelve years a considerable amount of work has been 
published, the greater portion of which comes from the pens of Molisch 
and Beijerinck. These two investigators, however, are chiefly concerned 
with the industrial processes and questions concerning the fermentative and 
bacterial action. 
Of work dealing more particularly with the localization of the indigo- 
forming substance within the plant there is comparatively little. The 
earliest suggestion of a method for indicating the situation of this substance 
within the plant occurs in the Botanische Zeitung for 1871 ( 3 ). Here 
Goppert, in dealing with the effect of frost on plants, notes that, when 
a flower of Phajus grandifolius , Lour., is killed by frost, part of the flower 
becomes blue. The fact is, however, only noted incidentally, and no effort 
is made to localize the indigo-forming substance. Attention is again 
drawn by Miiller-Thurgau ( 4 ) to this precipitation of indigo in the flower 
of Phajus grandifolhts , when it is killed by freezing. 
[Annals of Botany, Vol. XIX. No. LXXIV. April, 1905.] 
