176 American Midland Naturalist Monograph No. 2 



2. Leaves not white-margined; plants perennial with a deep root; roadsides, 

 fields, and open woods, common throughout 111. June-Sept. [Titby- 

 malopsis corollata (L.) Small} E. corollata L. 



2. Upper leaves conspicuously white-margined; plants annual; waste ground, 



escaped from cult.; native westw. July-Sept. \Lepadena marginata 

 (Pursh) Nieuwl.} Snow-on-the-mountain E. marginata Pursh 



1. Glands of the involucres without petal-like appendages. 



3. Leaves entire. 



4. Plants perennial, with a rhizome; stems clustered; capsules granular; 

 seeds smooth (seldom developing) . 

 5. Leaves lanceolate to linear, 4-15 mm. wide; waste places; nat. from 

 Eur. June-Sept E. esula L. 



5. Leaves linear, 1-3 mm. wide; roadsides and cemeteries; nat. from 



Eur. May-Sept. Cypress Spurge E. cyparissias L. 



4. Plants annual or biennial; capsules smooth; seeds pitted. 



6. Seeds finely pitted, 1-1.5 mm. long; lobes of the capsules 2-crested; 



waste places; nat. from Eur. June-Sept E. peplus L. 



6. Seeds coarsely pitted, 2 mm. long; lobes of the capsules rounded; 



wooded slopes and gravelly soil, local. May-June 



E. commutata Engelm. 



3. Leaves serrulate. 



7. Leaves spatulate; capsules warty; seeds smooth; moist ground in the n. 



half of the state. May-June E. obtusa Pursh 



7. Leaves obovate; capsules smooth; seeds reticulate; waste places; nat. 



from Eur. June-Oct. Wart Spurge E. helioscopia L. 



7. PoiNSETTiA Graham 

 1. Leaves chiefly opposite; plants pubescent, dull green; glands of the involucres 



stipitate; roadsides and fields, probably adv. from w. U.S. July-Sept. 



P. dentata (Michx.) Small 



1. Leaves alternate; plants glabrous or nearly so, bright green; glands sessile; 

 roadsides and waste places. June- Aug P. beterophylla (L.) Small 



95. Callitrichaceae Lindl. — Water-starwort Family 

 1. Callitriche L. — Water Starwort 



1. Fruit short-peduncled; bracts absent; plants terrestrial, growing on moist 

 soil, local; known from Champaign, Macoupin, St. Clair, and Wabash 

 counties C. an stmt Engelm. 



1. Fruits sessile; plants aquatic or amphibious. 



2. Bracts present. 



3. Fruit oval, flat, longer than the styles; known from Cook, Menard, and 



St. Clair counties C. palustris L. 



3. Fruit obovate, convex, shorter than the styles; local, throughout 111 



C. beterophylla Pursh 



2. Bracts absent; leaves all linear, submerged; St. Clair Co 



C autiimnalis L. 



