IOWA ACADEMY OF SCIENCES. 
141 
ERAGROSTIS PURSHII SCHRAD. 
(PI. xvi, Fig. 2; PL xviil, Figs. 16 and 16.) 
Epidermis. — The epidermal cells of both surfaces have thinner 
walls than in E. pectinacea. The cells vary considerably in size, 
those directly above or below a bundle being much smaller 
than those adjacent to the mesophyll. Stomata occur fre- 
quently on both surfaces, and the air spaces are large. Tri- 
chomes are longer than in any species except E. reptans^ and 
are thick, usually pointed. Above the intermediate bundles 
they occur in two or more rows. 
Bulliform cells . — These, four to seven in number, are large 
and quite evenly graded in size from the large central cell to 
the smaller outer cells. 
Mestome bundles number twenty one, of which sixteen are sec- 
ondary and five are intermediate in type. In the secondary 
bundles (vein 3) the chlorophyll bearing parenchyma sheath is 
nearly round in outline and composed of seven or eight subcir- 
cular cells. Hadrome, leptome and thick- walled parenchyma 
are not so well developed as in the preceding species. 
The intermediate bundles (carene and vein 2), five in number, 
are open below. Hadrome, leptome and thick-walled paren- 
chyma are well developed, the latter especially so. The chlo- 
rophyll-bearing parenchyma sheath is composed of from ten to 
fifteen cells. 
The mestome sheath is continuous above and sometimes 
below the secondary bundles, but is interrupted by stereome 
above the intermediate type. The carene is but little enlarged 
and not easily distinguished from vein 2 except by its position. 
Stereome is present in quantity both above and below the 
intermediate bundles and occurs in small groups of three or 
four cells in the secondary bundles. The mesophyll passes 
beneath some of the secondary bundles as a single layer of cells. 
ERAGROSTIS FRANKII MEYER. 
(PL xvi, Fig. 6; PL xvii, Figs. 10, 12 and 12a.) 
Epidermis . — Walls of the epidermal cells slightly thinner than 
in E. purshii. The epidermal cells of the inferior surface vary 
greatly in size, those beneath the bundles being much smaller 
than those beneath the mesophyll. Stomata are less frequent 
in this than in the other species. Trichomes are short, rounded 
or pointed, and occur on all bundles. 
Bulliform cells . — These are five or six in number, are more 
evenly graded in size than in any other species. 
