IOWA ACADEMY OP SCIENCES. 
143 
ERAGROSTIS MEXICANA. 
(PL xvi, Fig. 3; PL xvii, Figs. 7 and 8.) 
Epidermis . — The walls of epidermal cells intermediate in 
thickness between those of E. purshii and pectinacea. Epider- 
mal cells, small below the bundles and large below the meso- 
phyll. Stomata frequent on both surfaces. Trichomes short, 
thick, one-celled, occurring on all bundles. 
Bulliform cells, five to six in number, the central one large and 
broad. 
Mestome bundles. — There are forty-one mestome bundles, of 
the primary and secondary types. The primary bundles (carene 
and vein 2) are nine in number, with well- developed hadrome, 
thick- walled parenchyma and leptome, the latter surrounded by 
stereome. In the carene the chlorophyll- bearing parenchyma 
sheath is interrupted above the bundle by colorless parenchyma, 
but in the other primary bundles (vein 2) by thick- walled paren- 
chyma. 
The thirty-two secondary bundles are surrounded by a chlo- 
rophyll-bearing parenchyma sheath composed of eight or nine 
large cells, the two inferior cells having less chlorophyll than 
the rest. Leptome, hadrome and thick- walled parenchyma are 
not strongly developed. 
The mestome sheath is continuous above the secondary 
bundles (vein 3) but is interrupted in the primary bundles (vein 
2) by stereome or, in the carene, by colorless parenchyma. 
The carene is very large, the bundle being in the inferior 
part of it and subtended by a large quantity of stereome, while 
the upper part of it is filled by fifteen or twenty large cells of 
colorless parenchyma, flanked by mesophyll. 
Stereome is present in the usual quantity about the secondary 
bundles (vein 3) and in greater quantity above and below the 
primary bundles. Mesophyll is found abundantly in the carene, 
and as usual between the secondary bundles. Colorless paren- 
chyma occurs only above the carene bundle. 
ERAGROSTIS MAJOR HOST. 
(PI. xvi, Fig. 4; PI. xvii, Figs. 13, 14, 19 and 20.) 
Epidermis. — The walls of inferior epidermal cells are thick; 
those of the superior surface, as in E. mexicana. Stomata 
occur regularly on both surfaces. The trichomes are like those 
of the preceding species. 
