196 MR. P. GROOM—CONTRIBUTIONS TO THE 
explicable on the assumption that they prevent the escape of 
water and the entrance of hurtful fungi. 
In the larger and more completely drained rhizomes which I 
had, no scale-leaves were visible except in fragments, so that 
their original lines of insertion were visible and caused the 
annulation described by Blume. In addition, the tuber had 
become hollow. This may possibly have been the result of the 
immersion in methylated spirits, but appearances suggested that 
this hollow condition was occasioned before death, probably 
because the tubers supplied water to the inflorescence-axis more 
rapidly than they could absorb it from the soil. 
A comparison between Galeola and Epipogum nutans is 
instructive. 
Both are orchidaceous holosaprophytes. In Galeola the sub- 
terranean part is mainly constituted of the root-system. There 
are well-developed succulent roots, which act as the absorbing 
organs; these are coated for the most part by thick-walled cells, 
which would at first sight seem incapable of absorbing, and there 
are only very few stunted broad root-hairs. The scale-leaves 
possess a peculiar apparatus for storing water, and are primarily 
organs for getting rid of water. In Epipogum nutans there is 
absolutely no root-system ; the subterranean part of the plant 
is formed solely of a swollen tuber with scale-leaves. The 
absorbing organs are the scales, which send out innumerable 
greatly elongated hairs functioning as root-hairs; absorbed 
water is largely, or entirely, stored up in the water-storing cells 
of the rhizome, and there is no definite mechanism for getting 
rid of any excess of water when the plant is not flowering. 
Corresponding to the opposite functions of the subterranean 
scales in the two plants, their structure is very different. And 
the structure and the contents of the vascular bundles in or 
going to the scales vary in a like fashion. In Galeola there is à 
huge development of xylem in the scale. In Epipogum I could 
detect no bundles. In Galeola the regions of axis near the 
attachment are devoid of starch, and the leaf-trace bundles have 
no starch or very little. In Epipogum the leaf-trace bundles are 
markedly clothed with a sheath of starch-containing parenchyma, 
ihe starch in which is being conveyed to the central parts. 
In Galeola and Epipogum alike the absorbing organ is enveloped 
in a sheath of cells containing living fungal hyphe and no starch 
(exocortex in Galeola, scale-leaves in Epipogum). 
