62 Orr—LEAF GLANDS OF DIOSCOREA MACROURA. 
The mode of origin of these cell-filaments will be touched upon 
when dealing with the development of the gland, after the 
remaining features of the mature acumen have been disposed of. 
In the parenchyma, immediately adjoining the glandular tissue 
on its upper side, there are numerous air-channels, which follow 
the convolutions of the gland in a longitudinal direction, thus 
forming a complex aeration system. Each of these channels 
is enclosed by a definite sheath of parenchymatous cells. 
Likewise intimately associated with the glands are the vascular 
bundles, which lie parallel to them, and, at frequent intervals, 
send out smaller, lateral veins, which encircle the lower rim 
of each gland, being separated from the actual glandular tissue 
only by the parenchyma sheath. In these small vascular 
strands, there is no apparent inequality in the amount of xylem 
and phloem developed to meet the requirements of the gland. 
Ler 
25 
fa 
oe 
oP 
Fic, Blgrimdag ayn of the acumen of a young leaf, with developing gland. sc., 
cre sue, in proc See's : te f PiguiNe P ie ee 
f.. * flange” tion ; d., duct ; e., ‘‘corrugated epidermis ; 
ge” of tissue. x 350. a 
Here and there in the surrounding tissue, are to be seen large 
a oval cells, each containing a bundle of raphides, invested with a 
- mucilaginous envelope. Other cells containing tannin occur in 
‘ the mesophyll, just below the glands, and are particularly con- 
Spicuous in material fixed in chromic acid, Stomata are 
