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Birbal Sahni. 
mal walls give this reaction. Some of the endodermis cells were 
found to be traversed in the radial direction by peculiar struts 
(PI. IV, fig. 2) loosely attached by their flat ends to the respective 
tangential walls, and often becoming free by one or both ends. In 
unstained preparations, these objects appear homogeneously yellow 
and translucent. They stain bright red in gossipimine or safranin 
but remain unaltered in chlor-zinc-iodine. Their significance is 
obscure but they may serve a mechanical function similar to that 
ascribed by Schwendener 1 to the so-called Casparian strips on the 
radial endodermal walls of many plants. 
The cortex falls into two well-marked zones. The inner consists 
of about a dozen layers of cells. The walls of the layer immediately 
in contact with the endodermis are extremely thick, perforated by 
deep, straight pits, and thickly impregnated with phlobaphene. 
Eau de Javelle quickly bleached this substance ; the lamination of 
the walls became evident, and a violet colour with chlor-zinc-iodine 
showed the presence of cellulose. 2 The remaining cells of the inner 
cortex are large, and rounded or oval in cross-section, with 
abundant triangular inter-spaces. In the younger parts of the 
stolon, these cells have thin walls, numerous chloroplasts and 
large oval starch-grains. As the stolon becomes older the walls 
become thickened and pitted, and to some extent impregnated with 
phlobaphene, while the contents gradually disappear, the tissue 
assuming a purely mechanical function. 
The outer zone of the cortex consists of about ten layers of 
rather narrow cells with lignified 3 walls, closely packed without 
inter-spaces. In regions corresponding to overlying stomata, 
however, the cells of this otherwise air-tight sheath are thin-walled 
and loosely packed as in the lenticels of higher plants, and the 
sub-stomatal chamber is thus brought into communication with the 
air-system of the inner cortex. These channels persist long after 
the death of the stomata. 
2. The Secondary Stolon is, in the main features of its 
anatomy, very similar to the primary stolon, but bas a thinner 
xylem-core and relatively wide cortex, which is uniformly thick- 
walled, except for its one or two innermost layers which are left 
thin-walled. The air-space system is much reduced. In the 
endodermis, the “struts” (see above) are much shorter. The pericycle 
1 Haberlandt, “ Physiological Anatomy,” p. 371, Engl. Transl., 1914, 
2 Sperlich states that these walls are suberized in N. cordifolia (l.c., p. 467). 
3 This was confirmed by Wiesner’s phloroglucin and hydrochloric acid 
test, as well as by ammoniated fuchsin. 
