212 MR. P. GROOM— CONTRIBUTIONS TO THE 
rapidly and easily assume a new form and take on fresh functions.. 
This anticipation holds, at any rate, for the shoots of holo- 
saprophytes, and in particular for the leaves. This may be 
illustrated by a brief recapitulation of the functions and structure 
of the subterranean scales of the holosaprophytic orchids investi- 
gated and of Corysanthes. 
Gi.) Absorbing-organs.—Thin cell-walls, numerous long ab- 
sorbing-hairs, no stomata, no vascular bundles, but have leaf- 
trace bundles: mycorhizal hyphe present, e. g. Epipogum nutans. 
Gi.) Zranspiring or Water-excreting Organs.—No mycorhizal 
hyphe: well cuticularized epidermis. Vascular bundles. 
(a) Stomata: no hypodermal system of tracheides. Aphyllorchis 
pallida. 
(8) Stomata: a small bypodermal system of tracheides. Lecan- 
orchis malaccensis. 
(y) No stomata: thin-walled patches of epidermis: a large 
hypodermal system of tracheides. Galeola javanica. 
(iii.) Functionless, or merely temporary, bud-protectors. 
The lowest scale of Corysanthes has few stomata, no vascular 
bundle, and no leaf-trace goes towards it. The large scale higher 
up is larger, and has stomata and one vascular bundle. It is 
interesting to note that in Corysanthes the leaf-trace bundles 
and bundles within the scales have disappeared before the scales 
have been suppressed. This fact would seem to imply that 
leaves can entirely disappear in time without leaving any indi- 
cations of their former presence; not only in flowers but also in 
vegetative parts. 
Attention has already been directed to the histology of the 
vascular bundles of the shoot. It is, however, worthy of note that 
the plant which in the series investigated possesses the most 
reduced leaves and simplified vascular bundles is the hemisapro- 
phyte Corysanthes. This suggests that it is not the lack of 
chlorophyll which is most potent in inducing the structural modi- 
fications in holosaprophytes, but that ¿£ zs the habit of absorbing 
organic material which initiates the morphological changes: and 
one of these induced changes is the gradual disappearance of the 
chlorophyll. Amongst parasites the dwindling of the leaves is not 
necessarily associated with the loss of chlorophyll. There are a 
number of green parasitic genera in the Loranthacee and San- 
talacez which have species with normal foliage, and other species 
with tiny scales. The parasitic Cassytha has vivid green stems, 
but only minute scale-leaves. Many green autotrophic plants 
