302 Leake . — The Localization of the Indigo-producing 
7 . anil L. This plant was also growing in the Royal Botanic Garden, 
Calcutta, where the material was obtained. Indigo was precipitated 
abundantly in the mesophyll of the lamina. In the remaining tissues 
of the leaflet only traces occurred ; the distribution, however, is essentially 
the same as in I. arrecta y the difference is merely one of the degree of 
precipitation in the various tissues. The leaflets alone have been examined. 
7 . sumatrana , Gaert., and I. arrecta , Hochst. These two plants have 
been examined in greatest detail, and, since the distribution of the 
precipitated indigo is practically the same in both plants, they may be 
considered together. 
Leaf-lamina . In the lamina of the leaflet of both species there 
is a marked palisade-parenchyma beneath the epidermis of the upper 
surface and a spongy parenchyma of small cells, compactly set, with small 
intercellular spaces. Between these two normal kinds of parenchymatous 
tissue, or isolating on the side of the palisade-parenchyma a few cells 
of the spongy parenchymatous type, occurs a layer, one cell in thickness, 
of large, irregular cells with a small amount of protoplasmic content and 
relatively few chloroplasts. 
In all these varieties of parenchyma of the leaf-lamina indigo is 
precipitated, but it is especially abundant in the palisade-parenchyma, 
where it occurs as stellate masses either outlining a chloroplast, on the 
surface of which the indigo may be deposited, or suspended freely in the 
protoplasmic network of the cell (PI. XIII, Figs, i and 2). In the epidermis 
it also occurs abundantly, not only in the normal but in the two specialized 
types of epidermal cell — the guard-cells of the stomata and the epidermal 
hairs (Figs. 2-5). In the vascular bundles indigo is also abundant, and its 
distribution is best studied in the case of the midrib of the leaflet. Here 
the structure in no way departs from that of a normal leaf. The paren- 
chymatous tissue, especially on the dorsal surface of the leaf, is composed 
of thick-walled cells with little or no chlorophyll. In the vascular bundles 
fibres are present to a very limited extent, the vessels being separated 
by thin-walled parenchymatous cells rich in protoplasmic contents. 
In the xylem-parenchyma an abundant deposition of indigo is effected 
by the above-mentioned reagent. I11 the xylem-vessels alone is there 
no trace of deposition. Owing to the minute size of the elements of the 
phloem it is difficult to ascertain definitely where deposition actually takes 
place. A careful examination, however, shows that indigo may be present 
in all elements ; but the material is most unsuited for a clear demonstration 
(Fig. 6). 
In the extra-vascular tissue of the midrib indigo is again present 
in abundance, more especially in the thick-walled dorsal parenchyma 
(Fig. 6). 
The Rachis. The structure of the rachis differs from that of the mid- 
