192 MR. P. GROOM—CONTRIBUTIONS TO THE 
present in the infected cells of the hairs. In my alcohol- 
preparations the walls of many of these hairs had split into 
single spiral ribbon-shaped bands. 
Within this epidermis lie 2-3 layers of large parenchymatous 
cells (mesophyll), whieh are elongated longitudinally and rather 
flattened parallel to the surface; this suggests that conduction 
takes place down the scale-leaf rather than from the outer 
epidermis to the inner epidermis. 
The inner epidermis consists of small flattened cells. I failed 
to detect any vascular bundles within the scales, though leaf- 
trace bundles run in the rhizome to their bases. 
Gi.) Histology of the Rhizome-axis (Pl. VI. fig. 1). 
The fleshy axis itself is mainly constituted of large parenchy- 
matous cells with very thin walls. Though devoid of starch 
they contain more or less mucilage, but in the outer layers 
of the cortex some raphide-mucilage cells occur in addition. 
In the rhizomes richer in starch, several layers of cells with thin 
cellulose-walls occupy the position which would normally be 
taken by a general sclerenchyma-sheath ; they contain numerous 
grains of starch, and thus clearly mark out a general sheath 
(Pl. V. fig. 1. The parenchyma-cells immediately round the 
vascular bundles also contain starch. In the rhizomes from 
which much starch has been conducted up to the inflorescence- 
axis there is no accumulation of starch in a general (potential) 
sheath. This starch, like that in Monotropa, does not react 
typically with iodine-reagents. At first it colours red (varying 
from a dull red to a red-violet) probably because of the presence 
of erythrodextrin; with strong iodine the typical blue colour 
finally appears. Outside the general sheath the layers of cortex 
are devoid of starch; but the parenchyma around the leaf-trace 
bundles traversing this region of the cortex contains starch- 
grains. In the starch-containing cells I could see no trace of 
mucilage. Thus there appears to be a differentiation into water- 
storing cells and starch-containing cells. There are but few 
cortical layers outside the general sheath ; thus it is the greatly 
enlarged stele which makes up the main mass of the swollen 
rhizome. 
Each vascular bundle is collateral, and has a well-defined phloóm 
and xylem. The pAlozm (Pl. VI. fig.3; Pl. V. fig. 11) is greatly 
developed, and consists mainly of elongated parenchyma-cells, 
