170 MR. P. GROOM—CONTRIBUTIONS TO THE 
Thus, even if the fungus were harmless or even useful at first, it 
eventually kills the cells of the scales in the aeria] part of the axis. 
Histology of a Subterranean Scale (Pl. IV. fig. 5).—The main 
scheme of structure is the same as that of a bract, but the sub- 
terranean scale is much larger and the hypodermal system of 
storage-tracheides is disproportionately greater. These tracheides 
form, even immediately at the base of the scale, a large and close 
hypodermal sponge-work several layers thick. There are very 
few ordinary mesophyll-cells between the tracheides, which occupy 
a space as much as a third of the whole thickness of the leaf. 
In addition the tracheides display a strong tendency to arrange 
themselves with their long axes at right angles to the surface of 
the leaf, whereas in the bract the long axes are parallel to the 
surface. 
No hairs occur on these subterranean leaves. 
Function of the Leaves and Transpiration. 
In the absence of physiological observations, it is only possible 
to offer suggestions concerning the function of the leaves, the 
processes of transpiration and of absorption of solutions. 
The existence of well-developed xylem, mainly consisting of 
conducting tracheides, must be regarded as evidence for the 
existence of a considerable current of water from the absorbing 
parts to the growing portions of the plant. From analogy with 
other plants we must assume that the parts which absorb are 
those which contain mycorhizal hyphe. In spite of their thick 
walls, the roots and possibly portions of the rhizome absorb, the 
solution passing in through pits in the walls and probably 
especially by the agency of the mycorhizal hyphe. 
The question now arises as to how the plant gets rid of the 
excess of water absorbed. During a considerable portion of its 
existence, the plant consists merely of its subterranean portion 
(judging from the analogy of all investigated European sapro- 
phytes). Hence during that period the water cannot be disposed 
of by any aerial part of the plant. The solitary spots in the 
subterranean plant which are covered by thin and feebly cuti- 
cularized walls are the parts of the scale-leaves where a large 
hypodermal system of tracheides is developed. Hence I conclude 
that these scale-leaves are the organs of transpiration. It 
should be noted that these subterranean parts grow in positions 
liable to rapid changes in the moisture. In the first place the 
