IOWA ACADEMY OP SCIENCES. 
125 
BROMUS BREVIARISTATUS. 
(PI. iv, Pig. 1; PI. vii, Fig. 7.) 
Epidermis . — The epidermal cells are large and nearly rectan- 
gular, with a thick cuticle. The cells are a trifle smaller on 
inferior surface of leaf than on anterior, while on superior and 
inferior surfaces of mestome bundles they are much smaller 
than elsewhere. Conical projections occur both anteriorly and 
interiorly on primary mestome bundles. Stomata are present 
on both surfaces, while trichomes are long and quite abundant. 
Bulliform cells. — The bulliform cells are large and vary in 
number from three to six. 
Mestome bundles. — Forty-one bundles present, of two types. 
Those of the primary type are open on both inferior and supe- 
rior surfaces, i. e., leptome is in direct contact with stereome, 
while hadrome is separated from it only by colorless paren- 
chyma. These primary bundles vary much in size, and also in 
the amount of stereome and colorless parenchyma. The sec- 
ondary bundles are somewhat better developed in this species 
than in other species studied, in that both mestome and paren- 
chyma sheaths are present, also spiral and pitted ducts. There 
is an indication of an intermediate bundle at the margin of the 
leaf. 
Oarene . — Carene consists of only one bundle, and with the 
exception of size, the large amount of stereome and colorless 
parenchyma is exactly the same as those in the other species. 
Colorless parenchyma . — The colorless parenchyma occurs 
beneath all primary bundles, while a sheath encloses all the 
bundles. 
Stereome. — This is abundant on both inferior and superior 
surfaces of the primary type of bundles and on superior surface 
of the intermediate bundles. 
Mesophyll . — This surrounds all the secondary bundles and 
occurs between the other two types, and on the inferior portion 
of the intermediate type. 
EXPLANATION OP PLATES. 
All drawings made with a camera and drawn to the same scale. The abbreviations 
used are; 0., cuticle; E., epidermis; E. O., epidermal cells; Sto , stomata; Tr., tri- 
chomes; B. 0., bulliform cells; Ste., stereome; Mes., mesophyll; 0. B. P., chlorophyll- 
bearing parenchyma; Oar., carene: M. B., mestome bundles; H., hadrome; L,, leptome;^ 
Unc. Par., uncolored parenchyma; T. W. P., thick-walled parenchyma. 
Plate iv, Fig. 1, Bromus breviaristatus. Pig. 2, Bromus secalinus. 
Plate v., Fig. .3., Bromus patulus. Fig. 4, Bromus inermis. Pig. 5, Bromus asper. 
Plate vi. Pig. 6, Bromus patulus. 
Plate vii, Fig. 7, Bromus breviaristatus. Fig. 8, Bromus asper, 
Plate viii, Fig. 9, Bromus secalinus. Fig. 10, Bromus ineimis. 
