140 
IOWA ACADEMY OF SCIENCES. 
The mesophyll is normal, and the stereome rather small in 
quantity. 
ERAGROSTIS PECTINACEA GRAY. 
V 
(PI. xvi, Fig. 5; PI. xvil, Figs. 9 and 11.) 
Epidermis . — The cuticle of both surfaces is well developed. 
Walls of superior epidermal cells thicker than those of inferior 
cells. Epidermal cells of both surfaces more nearly equal in 
size than in any other species except E, replans. Stomata occur 
on both surfaces as in the preceding species. Trichomes short, 
thick, mostly blunt, of irregular size and occurence above the 
bundles. 
Bulliform cells. — From three to five in number, the central pne 
much the largest and flask* shaped, the long neck lying between 
the adjacent cells. 
Mestome trundles . — These are about fifty- seven in number. 
Forty- six are of the secondary type (vein 3) and eleven of the 
intermediate type (carene and vein 2). The chlorophyll- bear- 
ing parenchyma sheath of the secondary bundles is the most 
striking character in this species. It is distinctly triangular 
in outline, with the apex directed toward the superior surface. 
The lateral cells are elongated transversely to the section, and 
the inferior or basal cells are small and nearly round. Hadrome, 
leptome and thick-walled parenchyma are well developed. 
The intermediate bundles (carene and vein 2) are open below, 
with the leptome surrounded by stereome. The chlorophyll- 
bearing parenchyma sheath in these bundles does not have the 
triangular outline. Hadrome and thick-walled parenchyma are 
strongly developed. 
The mestome sheath in both types is interrupted above the 
bundles by stereome. The carene can be distinguished from 
the other intermediate bundles only by its position. 
/S'^ereome.— Stereome occurs below all bundles as a compact 
group of large cells, twenty to thirty in number, and above the 
bundles in small groups of three to six large cells. In some of 
these cells the cavity is in the form of an elongated oval. 
Stereome also surrounds the leptome in the intermediate 
bundles and extends upwards partiall}^ around the hadrome. 
The mesophyll presents no distinctive characters and col- 
orless parenchyma is absent. 
