GRASSES OF IOWA. 33 



to the secondary and five are intermediate. "In the secondary 

 bundles (veins 3) the chlorophyll-bearing parenchyma sheath 

 is nearly round in outline and composed of seven or eight sub- 

 circular cells. Hadrome, leptome and thick-walled paren- 

 chyma are not so well developed as in the preceding species. 

 The intermediate bundles (mid- nerve and veins 2), five in num- 

 ber, are open below. Hadrome, leptome, and thick-walled 

 parenchyma are well developed, the latter especially so. The 

 chlorophyll-bearing parenchyma sheath is composed of from 

 ten to fifteen cells. The mestome sheath is continuous above 

 and sometimes below the secondary bundles, but is interrupted 

 by sterome above the intermediate type. The mid-nerve is but 

 little enlarged and not easily distinguished from vein 2 except 

 by its position. Stereome is present in quantities both above 

 and below the intermediate bundles and occurs in small groups 

 of three or four cells in the secondary bundles. The meso- 

 phyll passes beneath some of the secondary bundles as a sin- 

 gle layer of cells. " 



In Mr. Ball's study of Eragrostis pectinacea, which is xe^^o- 

 phytic in its nature, a very striking chlorophyll parenchyma 

 sheath occurs near the secondary bundles. "It is distinctly 

 triangular in outline, with the apex directed towards the supe- 

 rior surface. The lateral cells are elongated transversely to 

 the section, and the inferior cr basal cells are small and nearly 

 round. Hadrome and leptome and thick- walled parenchyma 

 are well developed." 



We find a well marked type of bundle structure of leaf in 

 some of the mesophytic grasses represented by Festuca elatior 

 which has been described by Mrs. Hansen.* "The number of 

 mestome bundles in a single cross-section in middle of leaf is 

 twenty-four, and are not so close as in Lolium. There are 

 three types: First, primary type, open on inferior and supe- 

 rior sides. Second, secondary type, those that are entirely 

 closed, and these are most numerous. Third, the intermediate 

 type, which are open only on superior side. The bundles of 

 secDndary type are most numerous. Three of the closed bun- 

 dles occur near the margin of leaf. One bundle of the pri- 

 mary type is found next to the closed bundles. The third type 

 is found to the left of mestome bundle of mid-nerve, and to the 

 right of mid-nerve is found a mestome bundle of second type. 

 One primary mestome bundle occurs in mid-nerve. In the 



*1. C. 128: pi. 9,f. l.pl. tl,f.9. 



3 



