36 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



In 1887 M. xA.lvarez * attributed the formation of indigo to microbic 

 action. In the case of Indigofera tinctoria the organism in question 

 consists of a bacilhis 3 x 1*5 mm., rounded at the ends, in chains of from 

 6 to 8, surrounded by a gelatinous envelope. In old cultures the bacilli are 

 very motile, but less so in recent ones. They resemble the microbes of 

 Rhinoscleroma and the Pneumococcus of Friedlander, both of which 

 organisms Alvarez asserts are capable of setting up indigo fermentation. 

 In 1898 Breaudat t showed that with Isafis alpina micro-organisms i^layed 

 no part in the formation of indigo, because the change took place in weakly 

 alkalised chloroform water, as well as in water containing volatile oil of 

 mustard. He considered that the leaves contained a hydrated diastase 

 and an oxydase, the former of which in the presence of water reduces 

 the indican to indiglucine and indigo- white. The indigo- white is trans- 

 formed by the oxydase into indigo-blue in the presence of an alkali. 



Fig. 2. 



Apparatus devised by Heinrich for the extraction of indigo from Woad. The two 

 upper tubs are to contain, one, Woad leaves, which were first allowed to become 

 slightly dry, and water ; the splines seen on the top of the tub are to keep the Woad 

 leaves under water. The other tub is to contain quicklime and water to form lime- 

 water. After macerating some hours the contents of both these tubs were allowed 

 to run into the large tub in the centre of the picture. Here the liquids were mixed 

 and aerated by being allowed to run into the small tub in front and below, from which 

 they were raised by a small hand-pump as shown in the figure. At the end of the 

 process the precipitated indigo was drawn off by opening the taps at the sides of the 

 large middle tub.— From J. B. Heinrich's Culhir des Waids und die Indigobcnchtung 

 aus dieselhen. Wien, 1812. [For the opportunity of seeing this book my thanks 

 are due to Dr. Hans Molisch.] 



During the past summer a series of attempts to obtain indigo by 

 immersmg crushed Woad leaves in weakly alkalised water after the manner 

 recommended by Breaudat have been unsuccessful. The Woad leaves 

 were obtained from Woad cultivated in Lincolnshire and in Cambridgeshire, 

 from the Cambridge Botanic Gardens and from wild i^lants from 

 Gloucestershire. The result was, however, the same : not a trace of blue 

 colour would they, any of them, yield. A single exception is, however, 

 noteworthy. One plant from near Boston, put in water by itself, in a 

 glass specimen tube, turned blue without any special treatment ; many 



* XJomptc-Rendu Acad, des Sciences, ler aout 1887, t. 105, p. 287. 

 t Breaudat, L., "Sur le Mode de Formation de I'lndigo," Amiales d' Hygiene et de 

 Mddecine coloniahs, vol. i. 1898, No. 4, Oct.-Nov., p. 525. 



