144 
IOWA ACADEMY OF SCIENCES. 
On the margins of the leaves, and on the median nerve of the 
sterile and flowering glumes occur numerous small button- 
shaped projections — the scent glands. (PI. xvii, Pigs. 19 and 
20 .) 
Prof. Wm. Trelease^ says of these glands: “Morphologically 
the glands are epidermal structures consisting of a single layer 
of cells, the outermost of which are but little different from 
those of the adjacent epidermis, but gradually elongating ver- 
tically. 
Those at the center of the gland are considerably elongated 
at right angles to the surface, as is usual in epidermal secreting 
cells, but occasionally septate. While the peripheral cells 
have thick-pitted walls, and resemble the other cells of the epi- 
dermis in having transparent, watery contents, those at the cen- 
ter are much thinner- walled, and filled with coarsely granular 
yellow protoplasm. As compared with the unmodified epi- 
dermal cells, these elongated glandular cells are also thin- 
walled at top, where, in common with the other elements of the 
epidermis, they are invested with a rather heavy cuticle. In 
some cases this membrane is seen to be free from the crater of 
the gland in the form of a blister, while in others it had been 
ruptured, so that only fragments are present.” 
BulUform cells . — These are small in proportion, especially 
above the carene, and vary from four to six in number. 
Mestome bundles. — Thirty-one in number, of the secondary 
and intermediate types. Of the secondary tjpe (vein 3) there 
are twenty-four, surrounded by a chlorophyll-bearing paren- 
chyma sheath of eight or nine large cells, and containing lep- 
tome, hadrome, and thick-walled parenchyma. The intermediate 
bundles (carene and vein 2) are seven in number, open below, 
and contain strongly developed hadrome and thick-walled 
parenchyma, with leptome in greater quantity than usual, and 
entirely surrounded by stereome. 
The mestome sheath is continuous above the secondary bun- 
dles, but interrupted by stereome above the intermediate 
bundles of vein 2 and by colorless parenchyma above the carene 
bundle. • 
The carene is much enlarged and contains a few cells of col- 
orless parenchyma and considerable mesophyll. The latter is 
normal in quantity in the rest of the leaf. 
s The Glands of Eragrostis major, Host, Proc. Soc. Prom. Agr. Sci , 1889, p 70. 
