32 



GRASSES OF IOWA. 



Fig. 26. Section of leaf of Kragrnstis 

 purshii Schr&d. C'Up, superior surface; 

 Inf. inferior surface; Car, mid-nerve; 

 X/. leptome; H, hadroinf*; St. steromo; 

 MS, mestome sheath; Tr, trichome; B, 

 bulllform cells; Mes. mesophyll; BC, 



Fig. 27. DlKtichlis maritimn Raf ; MS, mestome sheath; 

 St, stereome; E. Ex epidermal expansions. (Holm.) 

 Section of b indle sh )wn below MS. mestome sheath; 



epidermal cells; C B. P. cdlorophyil St. stereome; C.B. P., chlorophyll baarlng parenchyma, 

 bearing parenchyma. (Ball.) (Holm.) 



"The secondary bundles differ in the marked line between 

 xylem and i)hloem and also in the nature of the sheath. This 

 consist of a single row of cells. Below and above the bundles 

 these have relatively smaller cavities and thicker walls than 

 the corresponding cells of Jouvea pilosa. but frequently on 

 either side of the bundle there 02curs one cell much larger 

 than the others^ of more angular shape, and in almost any sec- 

 tion taken at random a transverse pitted wall is conspicuous. 

 The two uppermost cells of the inner chlorophyll-bearing ring 

 are at least twice as large as the other cells of the ring, and 

 are usually wecJge-shaped with the narrow end turned towards 

 the bundle." 



Mr. C. R. Ball, || in an interesting study of the leaves of sev- 

 eral species of Eragrostis, well describes the mestome bundles 

 of Eragrostis pursJtti, which number twenty-one. Sixteen belong 



IIAn anatomical study of the leaves of Eragrostis. Proc. la. Acad. Scl., 4: 140-Hl, 

 1897. pi. 7. f. 2, 3 and 4; pi. 9. f . t:. Contr. Bot. Dept. la. .'^c. Coll. Agrl. and Mechanic 

 Arts, 4. 



