(501 ) 
the idea that, like tannin, it serves as a defensive against insects and 
snails. But this supposition would explain only the function of the 
indican but not that of the splitting products and the indigo-enzyme. 
If a beneficient influence on the growth in general could be ascribed 
to indoxyl, then a useful action of this substance on the curing of 
hurt parts would become probable. And this would also spread more 
light on the function of the indican and the enzyme, for then it 
would be clear that the enzyme-action, which operates at the very 
dying off of the hurt cells, would promote the curing, not only by 
the formation of indoxyl but also by the production of glucose. 
As to the localisation in the cell, I found the leaves of Phajus 
grandiflorus by their broad-celled structure fit for demonstrating 
microchemically indican as well as indigo-enzyme. 
The indican can be precipitated as indigo-blue or indigo-red, and 
both ways point out that it is present in the protoplasm and wanting 
in the cell-walls, cell-nuclei, and cell-sap. To demonstrate this a not 
too thin microscopic transverse section of a leaf is put in living 
condition in a boiling mixture of strong hydrochloric acid and ferri- 
chloride. The indican is suddenly decomposed and the freed indoxyl 
as quickly oxidized into indigo-blue, which is easily detected under 
the microscope as a precipitate in the shape of small blue granules 
in the colourless protoplasm of the green parenchyma and the 
epidermis. I could not trace it with certainty in the chlorophyll- 
granules. 
If the sections, in living condition, are put in a boiling mixture 
of hydrochloric acid and isatine, the indican passes into indigo-red, 
which sets off in the protoplasm as very characteristic red crystal 
needles '). 3 
The enzyme, on the contrary, is exclusively accumulated in the 
chlorophyll-granules as is proved by the following. 
If living microscopic sections of leaves of Phajus are put in 
an indican-solution (e. g. in a decoct of Indigofera or Polygonum) 
they become blackish blue in a short time, which colour is 
exclusively caused by indigo-blue precipitated in the chlorophyll- 
granules. In the epidermis much indigo is precipitated only in 
1) The presense of indoxyl in urine may be shown with much more certainty and 
exactness in the form of indigo-red than of indigo-blue. To this end the urine is 
boiled with hydrochloric acid and isatine by which the colour grows red. At cooling 
the indigo-red crystallises in characteristic microscopic needles. These are easily 
filtered and dissolve beautifully red in alcohol (best is to boil out the whole filter 
with alcohol). 
