IOWA ACADEMY OF SCIENCES. 
131 
Bulliform cells . — The bulliform cells are not greatly differen- 
tiated. In a great many cases the cells are hardly to be distin- 
guished fro m epidermal ceils proper. They occur between each 
mestome bundle and number three. 
In the middle of the leaf there are from thirty to thirty-three 
mfestome bundles of three types: primary, secondary and inter- 
mediate. 
The mestome bundles of secondary type are most numerous, 
sixteen in each leaf. These bundles are rather small, and occur 
near the margin of the leaf. Those of the secondary type 
consist mainly of thick-walled cells with poorly developed 
pitted vessels. One mestome bundle of second type occurs on 
each side of mestome bundle of carene. 
Three sizes of mestome bundle of first type occur. One is 
found in the carene. This is the largest; other sizes follow in 
numerical order, beginning from margin. The smallest is shown 
in plate IX. 
In the two larger, the leptome and hadrome is well developed, 
aad in the smallest bundle the spiral duct in some instances is 
wanting. 
Stereome . — This is quite conspicuous in the carene. Hadrome 
separated from stereome by colorless parenchyma cells. In 
carene the stereome is more strongly developed on inferior 
than on superior surface of mestome bundles. The mestome 
bundle of second size has the stereome not so well developed on 
its superior and inferior surfaces as is found in carene. The 
mestome bundle of third type is of the same size as the smallest 
of the first type, only they are more numerous. 
Stereome is found on the margin of leaf, and numbers from 
four to six cells; it also occurs on superior and inferior surfaces 
of all bundles, except those of the second type. It does not 
occur on either superior or inferior surface of the bundles of 
second type. 
Mesophyll . — ^This occurs between all mestome bundles. The 
cells are quite uniform in size. 
EXPLA.NATION OF PLATES, 
All drawings were made with the camera, and are drawn to the same scale. The 
abbreviations used are: 0., cuticle; E, epidermis; E. C., epidermal cells; Sto., stoma; 
Tr , trichomes; B., bulliform cells; Ste., stereome; Mes., mesophyll; 0. B. P., chloro- 
phyll-bearing parenchyma; Oar., carene; M., mestome bundles; H., hadrome; L., 
leptome. 
Plate ix, Pig, 1, Festuca elatior, var. pratensis. Fig. 2, Festuca tenella; Fig. 3, 
Lolium perenne; Fig. 4, Bromus patulus. 
Plate x, Pigs. 5 and 6, Festuca tenella; Fig. 7, Bromus patulus. 
Plate xi. Fig. 8, Lolium perenne; Fig. 9, Festuca elatior, var. pratensis. 
