138 
IOWA ACADEMY OF SCIENCES. 
AN ANATOMICAL STUDY OF THE LEAVES OP 
ERAGROSTIS. 
BY CARLETON R. BALL. 
This study was undertaken in order to ascertain if the anat- 
omical characters in the leaves of this genus were sufficiently 
well marked and constant to be of value in identifying the dif- 
ferent species. The results of similar studies by others have 
been encouraging. Prominent among these is the series of 
excellent papers by Theodore Holrn^ who has studied six genera- 
Uniola, Distichlis, Fleuropogon, Leersia, Oryza, and AmpMcarpum^ 
and considers the anatomical characters of all except Distichlis 
to be a reliable basis for determining the different species. 
Emma Sirrine and Emma Pamme? have studied Sporobolus and 
Panicum and conclude that the species in these genera, so far as 
studied, may be differentiated by means of their anatomical 
structure. 
In this paper the author has considered six species of Era- 
grostis, viz, : E. reptans Nees, E. pectinacea Gray, E. purshii 
Schrad., E. franlcii Meyer, E. mexicana and E. major Host. 
In these species three structural types of mestome bundles 
occur: primary or open bundles (PL XVII, Fig. 8.) in which the 
chlorophyll- bearing parenchyma sheath is found only at the 
sides of the bundles and is wanting above and below them; sec- 
ndary or closed bundles (PI. XVII, Fig. 13, vein 3,) in which this 
sheath completely surrounds the bundle, separating the lep- 
tome from the stereome below and the hadrome and thick- 
walled parenchyma from the stereome, mesophyll, or paren- 
chyma above; intermediate bundles in which this sheath is 
interrupted either above or below the bundle. 
1 A Study of Some Anatomical Characters of No. Am. Graminece, Bot. Gaz., Vol. 
XVI, pp. 166, 217, 275; Vol. XVII, p. 358; Vol. XX, p. 362; Vol. XXI, p. 357; Vol. XXII, 
p. 403. 
2 Some Anatomical Studies of the Leaves of Spo obolus and Panicum, Proc. la. 
Acad. Sci., 1895, Vol. Ill, p. 148. (An extended bibliography of this subject may be 
found in this paper.) 
