64 OrR—LEAF GLANDS OF DIOSCOREA MACROURA. 
“twin’’ glands diverge, and the process is repeated until all the 
glands found in the fully-developed organ have come into 
existence. At a later period of development, the epithelium 
forming the roof of the gland becomes extensively folded, owing 
to the excessive multiplication of the cells composing it, which 
has the effect of increasing the internal area of the gland-cavity, 
while, externally, the hollows between the folds are filled in by 
the unequal growth of the adjoining ground tissue. 
Bo 
eax 
vA 
a 
Ren he 
FiG. 3.—Transverse section of a portion of the glandular region at the base of a developing 
acumen, showing two immature glands, which have been formed by the sub- 
division of the original gland cavity. sc., secretory tissue; d.d., ducts; e 
pidermis ; f., base of ‘‘ flange.” x 350. 
Meanwhile, other cells of the peripheral layer encircling the 
lower half of the gland undergo tangential division to form the 
compact, parenchyma sheath, which, together with tne epithelial 
layer, separates the lumen of the gland, on its under side, from 
the associated vascular tissues, and the adjacent less-compacted 
mesophyll. 
The very young leaf, and its acumen, are covered with minute, 
multicellular scales, which are most obvious in sections of the 
bud, where they appear immersed in the deeply-staining fluid. 
They are notably evanescent, and are wanting in the fully- 
developed leaf. These epidermal outgrowths bear a striking 
resemblance to the immature secretory elements, which are, 
