358 IOWA ACADEMY OF SCIENCE Vol. XXV, 191S 



scabrous, pointed, narrow and numerous; sheaths long; ligule 

 narrow, lacerate; collar wideniuii- at either marLnn ; auricle want- 

 ing. 



Fig. 134. — Mnhlenbergia racemosa. Marsh Muhlenbergia. A, ligule : B, 

 collar ; C, base of dead culm, and base of new shoot ; D, dead culm of previous 

 year's growth ; E, new rhizome ; F, rhizome scars. 



Pamcum Scribnerianiint. Scribuer's panicuin. Figure 135. 



A very erect perennial with a slender, very vigorous, creeping, 

 almost white rhizome. The nodes are not conspicuous. New 

 shoots arise in somewhat uniform growth from buds at the nodes 

 but first appear at extremes of growth. Roots are long, rather 

 tough, but not especially numerous. Leaves rolled in bud, blade 

 flat, slightly scabrous, one-half to three-fourths cm. wide, sharp, 

 pointed, glabrous. Sheath loose, striate, sometimes slightly pub- 

 escent. Ligule acute, slightly toothed. Auricles wanting. Collar 

 broadened at margins, narrowed in middle. 



Panicum virgaiimi. Switch Grass. Figure 136. 



An erect perennial. Rhizome creeping, very tough, one-eighth 

 to one fourth inch in diameter, scales conspicuous. The new 

 shoots do not come from the terminal end of the old rhizome. 

 New shoots may spring from base of old culms ; new buds aris- 

 ing from nodes of rhizome are twisted, growing obliquely until 

 they reach the surface of the ground. Roots few but long and 

 coarse. Leaves glabrous, rolled in the 'bud, which is cylindrical. 

 Sheaths ciliate along margin at the top, smooth, not compressed. 

 Blade flat, narrowed at the base, one-eighth to one-half inch 



