300 American Midland Naturalist Monograph No. 7 



802; also in Missouri. Native of trop. Asia 



....S. oligorhiza (Kurz) Hegelm. 



3. Wolffia Horkel 

 1. Plants globose or ellipsoid, not flattened, 0.5-1 mm long, loosely 

 cellular, not punctate, floating somewhat beneath the surface; 



locally abundant in stagnant water W. columbiana Karst. 



1. Plants flattened on the upper surface, brown-punctate, compactly 



cellular, floating at the surface of the water. 



2. Plants 1-1.5 mm long, rounded ovate, strongly gibbous, the 



upper surface with a central conical papilla; in permanent 



pools of stagnant water, rare; Wabash Co., Schncck; Union 



Co., Swaync 1890 W. papulijera C. H. Thompson 



2. Plants 0.5-0.8 mm long, ellipsoid, slightly gibbous, symmetrical, 

 the upper surface flat or slightly convex, gradually rising to 

 the acute apex; stagnant water, rare; Hancock, Jackson, 

 Menard, and Sangamon counties W. punctata Griseb. 



4. Wolffiella Hegelm. 

 W. fioridana (J.D.Sm.) C.H.Thompson. Stagnant water, rare; 

 Alexander and Union counties. 



143. Typhaceae J. St. Hil. — Cat-tail Family 

 1. Typha L. — Cat-tail 



1. Leaves 1-2.5 cm wide, light green, nearly flat; staminate and pistil- 

 late parts of the spike usually contiguous, the latter becoming 

 2-3 cm in diameter at matmuty; pollen grains in loms; stigma 

 spatulate; marshes, margins of ponds, and along ditches, com- 

 mon throughout 111. June-July. Common Cat-tail 



T . latifolia L. 



1 . Leaves 4-8 mm wide, dark green, convex on the back ; staminate 

 and pistillate parts of the spike separated by a short interval, 

 the pistillate part only 10-18 mm in diameter; pollen grains 

 simple; stigma linear; marshes, less common than the preceding 

 species. June-July. Narrow-leaved Cat-tail T. angustijolia L. 



144. Sparganiaceae J. G. Agardh — Bur-reed Family 

 1. Sparganium L. — Biu-reed 

 1. Achenes obpyramidal, truncate at the summit, sessile; stigmas 

 usually 2; ditches and margins of ponds. June-Jidy. Giant Bur- 

 reed .S". eurycarpum Engelm. 



1. Achenes fusiform, stipitate; stigina L 



2. Pistillate heads all strictly axillary, 2-2.5 cm in diameter at 

 maturity; beak of the matiue achene 2-3 mm long; leaves 6- 

 12 mm wide. 

 3. Inflorescence branched; stigmas 2-4 mm long; ditches, rare 

 S. androcladum (Engelm.) Morong 



