142. Lkmnaceak 299 



1. Leaflets 7-11 ; spadix slender, piojecting beyond the green spathe; 

 moist woods, common. May-June. Green Dragon. Dragonroot 

 A. (Iracoiitiiini (L. i Schott 



2. Symplocarpus Salisb. — Skunk-cabbage 

 S. foetid us (L.) Nutt. Swamps, local; chiefly in n.e. and central 

 111., extending southward to Jasper C'o. Feb. -Apr. 



3. Peltandra Ral. 

 P. virgiiiica (L.) Kunth. Muddy margins of ditches and ponds, or 

 in shallow water, or swamps, local; extending northward to Kankakee 

 and Peoria comities. May-June. 



4. Acorus L. — Sweetflag 

 A. calamus L. Swamps or wet ground along streams, locally nearly 

 throughout 111. June-Aug. Probably native in 111. and elsewhere in 

 U.S., although introd. into Eui'. as early as 1557. 



142. Lemnaceae Dumort. — Duckweed Family 



1. Plants witli roots. 



2. Root solitary, without vascular tissue 1. Lemna 



2. Roots 2-several, each with a vascular bundle 2. Spirodela 



1. Plants without roots. 



3. Plants thick, ellipsoid to subglobose 3. Wolffia 



3. Plants thin, ligulate 4. Wolffiella 



1. Lemna L. — Duckweed 

 1. Plants paddle-shaped, 6-10 mm long, remaining connected, wholly 



submerged; ponds and ditches, local L. trisulca L. 



1. Plants oval or roundish, 2-5 mm long, soon separating, floating. 

 2. Plants narrowly elliptical, often somewhat falcate, 0.5-1.5 mm 

 wide, obscurely 1-veined, smooth; ponds and swamps, rare, s. 



111. [L. cyclostasa of auth.] L. valdiviana Phil. 



2. Plants suborbicular to ovate, 2-5 mm in diameter. 



3. Plant-body asymmetrical; i-oot-tip pointed; seeds orthotro- 



pous; ponds and streams, local L. perpusilla Lorr. 



3. Plant-body symmetrical or nearly so; root-tip roimded; seeds 

 amphitropous; stagnant water and slow streams; probably 

 the most prevalent species in 111. [incl. L. iniu'uua of auth.] 

 L. minor L. 



2. Spirodela Schleid. 

 1. Plants roundish-obovate, 3-8 mm long, 5-11 -nerved; roots 6-18; 



ponds, ditches, slow streams, locally abundant 



^S". polyrhiza (L.) Schleid. 



1. Plants elliptical, 2-4 mm long, obscurely nerved; roots usually 2 or 



3 (rarely 6) ; Horseshoe l,ake, Alexander Co., F. H. Daubs 545, 



