278 Ewart. — On the Leaf-glands of 
These basal polygonal cells fit closely one to another, and 
their side-walls are thickened and slightly cuticularized, staining 
a deep orange-brown with iodine and with chlor-zinc-iodide. 
Fig. 17 represents a tangential section (parallel to the 
secreting surface) across a bundle of secretory cells, and 
Fig. 1 8 a similar section at a lower level, across the polygonal 
cells. 
Immediately below each polygonal cell is another cell 
(Fig. 1 6, has 2 ), having much thinner walls of cellulose, not 
flattened, but nearly as deep as broad ; and adjoining this 
deeper layer (das 2 ) is the small-celled parenchyma forming 
the ‘packing’ of the gland, which gradually merges, after two 
or three layers, into the. large loose ground-tissue of the leaf. 
The walls of all the parenchymatous cells are marked by 
numerous large simple pits. 
The cells of the secretory epithelium are partly filled with 
granular protoplasm, which contains large vacuoles ; in the 
fresh leaf they have a swollen appearance (s.e., Fig. 16). The 
nuclei are large and fairly distinct, often showing a nucleolus. 
The outer walls of the cells are very thin. Each bundle of 
secretory cells is conical, the narrow base resting on the single 
basal cell, while the wider free extremity fits closely with its 
neighbours over the rounded curves of the much-folded gland. 
Transverse septa occur here and there in some of the older 
epithelial cells, but the majority appear to be undivided. 
The two basal layers of cells (das 1 , das 2 , Fig. 16) present 
a great contrast to the bundles of cells above them ; they 
contain comparatively little protoplasm, and very large 
vacuoles, and a distinct nucleus. They have a clear transparent 
appearance, especially those of the upper row (das 1 ), whose 
walls are so much cuticularized that they seemed in section 
to form a firm hard wall shutting off the secretory epithelium 
from the cells beneath. The lower cell-walls of the second, 
deeper row are thin and cellulose in character, and communi- 
cate by pits with the small-celled parenchyma below. 
Since examining these glands of Ipomoea , my attention was 
called to Macfarlanes description of the secreting glands of 
