ORR—LEAF GLANDS OF DIOSCOREA MACROURA. 59 
enclosing the glands, the latter roofing over the interposing 
veins. 
The innermost pair of these glandular ridges extends practi- 
cally the whole way from the base of the acumen to its apex, 
but those more lateral in position, by a repeated process of 
fusion with their immediate neighbours on the inner side, lose 
their identity in turn, until all are merged in the two innermost, 
persistent, glandular tracts. 
Near the margins of the acumen, there project, from its upper 
surface, two thin flanges of tissue, which, in the older leaves, 
are directed outwards; but, in the younger leaves, the entire 
marginal portions of the acumen, from which the flanges arise, 
bend inwards, and completely enclose the upper surface and its 
longitudinal slits. As the leaf matures, the involuted margin 
gradually unfolds, and the slits become exposed, . 
The disparity in size between the young leaf and its acumen 
is very marked, for example, an undeveloped lamina, 7 mm. 
long, may be surmounted by a tail-like tip of 40 mm. in length. 
It does not follow, however, in spite of this disproportion in 
size, that the acumen necessarily becomes physiologically 
functional before the lamina reaches maturity, for it can be 
shown that, at this stage, the glands of the acumen are still 
in process of formation, and they only reach their highest state 
of development when the leaf-blade has expanded to more nearly 
its adult proportions. 
Before proceeding to a consideration of the anatomy of this 
specialised organ, it might be well, at this point, to refer briefly 
to some of the technical methods employed. 
The fluids used for the fixation of the parts to be examined 
were acetic-alcohol and chromo-acetic solution, and the material 
was embedded in paraffin, and sectioned by means of a micro- 
tome. By piecing together the serial sections obtained by 
cutting the material in different directions, it was possible to 
secure a mental picture of the convolutions of the glandular 
svstem, which was helpful in elucidating its construction. 
Various stains were employed, but perhaps the best results were 
obtained by using safranin, iron-alum haematoxylin with a 
contrasting stain, or a combination of gentian-violet and eosin. 
For the examination of the micro-organism present in the glands, 
the usual bacteriological methods of staining were followed. 
The general anatomy of the leaf-tip can best be illustrated 
by reference to Plate CXCVII, which is a photograph of the 
_transverse section of a medium-sized acumen, cut from near the 
apex. In this, the position of the glands, their relationship to 
ae the other tissues, and the general configuration of the organ 
are clearly demonstrated, 
