IOWA ACADEMY OP SCIENCES. 
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stereome by several rows of thin-walled parenchyma cells. 
The stereome is more strongly developed on the inferior sur- 
face of mestome bundles of carene than than on superior surface 
of bundle. In carene the stereome is not in contact with lep- 
tome. 
A thin- walled parenchyma sheath surrounds the entire 
bundles of secondary type. Thick-walled cells occur on the 
inside of this parenchyma sheath, which thus forms a sheath 
around the leptome and hadrome. 
Two kinds of mestome bundles of secondary type occur, one 
in which leptome and hadrome are perfectly developed, and a 
second in which leptome and hadrome are not so strongly 
marked. Those of the second type alternate with the large 
bundles. These bundles are surrounded by a chlorophyll-bear- 
ing parenchyma sheath. To the inside of this sheath is a sec- 
ond sheath which consists of thick-walled cells (mestome sheath) 
surrounding the leptome and hadrome, and hence is closed. 
The mestome bundles of intermediate type are four in number, 
and do not vary from the mestome bundle of prim.ary type 
except that they are closed, and there are only two pitted ves- 
sels. 
Stereome.— stereome is found on margin of leaf on super- 
ior surface of all bundles of intermediate and primary types, 
and on the inferior surface of some of the mestome bundles of 
secondary type. 
Mesopliyll.—This, occurs between the mestome bundles, and 
is in contact with the epidermis on both faces. The cells are 
irregular, some are nearly round, others are oblong. The 
chlorophyll grains are large. The cells of the mesophyll on 
margins of leaf are somewhat smaller than in other parts. 
PESTUCA. 
Two species of Festuca were studied. Festuca elatior^ variety 
pratensis, and Festuca tenella. 
Beal quotes Hackel’s statement as to the different forms of 
Festuca: “Hackel finds the mesophyll and fibro vascular bun- 
dles quite uniform with all sorts of treatment of the plants, but 
the epidermis offers remarkable differences, especially that on 
lower surface of leaf. This difference is apparent in the thick- 
ness of the outer walls, the size of the cavities, and the exist- 
ence or absence of projections on the partition walls. The dry 
cultivated plants had their epidermis strongly thickened toward 
the outside, the cavities diminished and over the partition wall 
