KNOWLEDGE OF MONOCOTYLEDONOUS SAPROPHYTES. 199 
‘below the foliage-leaf, is a second scale (s"), in the axil of which 
is a well-marked bud. Thus the three leaves have a distichous 
arrangement. This erect axis at its lower end is attached to a 
tuberous body which is feebly bilobed and is less hairy than the 
axis. Near the junction of the tuber and the erect rhizome 
‘several (2-3) hairy root-like processes radiate, and arise, from the 
tuber. So much can be seen with the naked eye. 
Histology of the Tuberous Body. 
In the tuber there is a regular external layer having its thin 
walls cuticularized, but with no stomata. Many of the cells grow 
out to form long slender unicellular hairs with cuticularized 
walls. For the most part fragments of humus do not cling to these 
hairs, which are not irregular or lobed; but humus adheres to 
some of the hairs, which are furthermore irregular in contour or 
even lobed towards their extremities. Straight hyph: occur in 
many of the hairs; also hyphæ occur in some of the general cells 
of the external layer, some of which are discoloured. But no 
coiled mycorhizal mycelia are found. Beneath the superficial layer 
is a well-defined exodermis (Pl. V. fig. 12), constituted of cells 
with thin suberized walls. I failed to detect any special passage- 
cells. Within the exodermis succeed about ten layers of cortical 
parenchyma, the cells of which are large and are crammed with 
large starch-grains. In the centre of the tuber is a dispro- 
portionately narrow stele with small vascular bundles. The 
endodermis is thin-walled, and is succeeded by a single layer of 
pericycle. Typically the stele may be described as triarch, 
though allsections do not display the same arrangements. There 
are three small groups of xylem, in the form of spiral-reticulate 
tracheides, which dip deeper towards the centre than do the 
three groups of phloém. 
Histology of the Rhizome below the attachment of the 
Upper Scale. 
An epidermis with thin cuticularized walls forms the external 
layer. Amongst the cells are scattered stomata which gape open 
and are normal in appearance. 
The surface is raised into many multicellular cylindrical or 
conical outgrowths. The terminal cells of these grow out into 
usually four or five (4-8) long hairs (PI. VI. fig. 6). Typically the 
multicellular outgrowth consists at its base of an axial row of 
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