304 Leake.— The Localization of the Indigo-producing 
absence of blue. Of the corolla, the carina and vexillum show only the 
merest traces of blue deposition. No deposition could be traced in the 
alae of /. sumatrana ; but in I. arrecta these contained a sufficient quantity 
to give a faint coloration, barely perceptible with the naked eye. In 
neither case did the filaments of the stamens show any trace of blue. 
The walls of the ovary up to, and shortly after, fertilization show a con- 
siderable deposition in the parenchymatous cells, as do the highly meri- 
stematic cells of the ovule of both species at the time of, and shortly after, 
fertilization. This applies to each of the component parts of the ovule, 
to the integuments, the nucellus, and even to the embryo-sac (Fig. 11). 
Shortly after fertilization all trace of blue vanishes from all parts 
of the ovary, nor does it appear in the ripe seed. 
II. ISATIS TINCTORIA, L. 
Owing to the fact that a temperate climate is best suited to the 
growth of this plant, it has supplied the material for some of the most 
detailed work which has so far been carried out, both on the subject 
at present under consideration and on the biological and fermentation 
problems connected with indigo and its formation from plant tissues. 
Molisch in 1893 ( 5 ) used for a macrochemical investigation dilute 
ammonia. In localizing the blue-forming substance by alcohol vapour 
he finds traces in the roots, except those of flowering plants and of plants 
under fourteen days old, and in the cambium and epidermis of the stem. 
As regards the leaves he says : ‘ Schon die beiden im Lichte ergriinten 
Keimblatter und die jungen, die Plumula umhullenden Primordialblatter 
enthalten sammt dem Vegetationspunkte des Stengels reichlich Indican.’ 
He further locates the precipitated indigo in the epidermis, mesophyll, and 
those elements of the vascular bundles which have protoplasmic contents, 
especially the latter, so ‘ dass die ganze Nervatur als blaues Netz in Er- 
scheinung tritt.’ In the cotyledons it is present, while the flower-buds, but 
not the opened flower, contain a deposit of indigo. 
In repeating the investigation in 1899 (8) he uses ammonia instead of 
alcohol-vapour. The position of the blue, as here described, differs some- 
what from that previously allotted to it. The chlorophyll granules of the 
mesophyll stand out a deep blue. In the epidermal hairs and the epidermis, 
with the exception of the guard-cells and a few of the cells bordering 
on the guard-cells, only traces are present. The vascular bundles also 
show only traces. 
Beijerinck, in 1900 (10), localizes indigo ‘besides in the young leaves 
and buds, also in the young root-peridermis, in the root-buds and in the 
growing root-ends.’ It is absent in the thick stems and all the thicker 
