E UP HO RBI A CEA E. 5 9 1 



Bracts and leaves of the umbel small and green; seeds ovoid, smooth, sparingly pitted. 

 Pale green ; leaves all whorled or opposite. 17. E. Marylandica. 



Deep green; leaves below the umbel alternate. 18. E. corollata. 



Bracts and leaves of the umbel large, white-margined: seeds ovoid-globose, reticulate- 

 tuberculate. 19. E. matginata. 



* * Glands of the involucre without petal-like appendages, 

 f Leaves mostly opposite; herbage glabrous. 

 Plants slender; stems or branches forked. 



Annual; stem branched at the base; leaves, or some of them, oblique at the base. 



1. E. polygoni/olia. 

 Perennial; stems several from a stout root ; leaves not oblique at the base. 



22. E. Ipecacuanhae. 

 Plants stout; stem usually simple below, topped by an umbel. 24. B. Lathyris. 



f f Leaves mostly opposite ; herbage pubescent. 

 Leaves linear or linear-lanceolate; seeds narrowly ovoid, not prominently tuberculate. 



20. E. caphosperma. 

 Leaves ovate or ovate-lanceolate; seeds broadly ovoid, prominently tuberculate. 



21. E. dent at a. 

 f f f Leaves alternate or scattered. 



Stem not topped by an umbel. 23. E. heterophylla. 



Stems topped by a several-rayed umbel. 



Leaves serrulate; glands of the involucre oblong, oval or orbicular. 

 Seeds smooth or faintly reticulated. 



Glands stalked; warts on the capsules elongated; seeds faintly reticulated. 



26. E. obtusata. 

 Glands sessile; warts on the capsules depressed; seeds smooth. 



27. E. platyphylla. 

 Seeds strongly and prominently reticulated. 



Glands nearly sessile; capsules warty. 



Upper leaves merely sessile; upper bracts of the umbel manifestly 



longer than broad. 28. E. Arkansana. 



Upper leaves with small basal lobes; upper bracts of the umbel 

 about as broad as long or broader. 29. E.Missouriensis. 



Glands stalked; capsules smooth. 30. E. Helioscopia. 



Leaves entire; glands of the involucres crescent-shaped or reniform. 

 Annual or biennial; seeds pitted. 



Capsules with 2-crested lobes. 31. E. Pep/us. 



Capsules with rounded lobes. 32. E. commutata. 



Perennial. 



Glands reniform or oblong, without horns. 25. E. Darltngtonii. 



Glands crescent-shaped, with horns. 



Seeds smooth; glands with long slender horns. 



Stem-leaves 4-12 mm. broad; capsules smooth. 



Bracts subtending the umbel lanceolate to oblanceolate. 



33- E. Esula. 

 Bracts ovate, oval or obovate. 34. E. lucida. 



Stem-leaves 0.5-3 mm « wide; capsules with granular lobes. 



35. E. Cyparissias. 

 Seeds pitted; glands with short rather blunt horns. 36. E. robusta. 



I. Euphorbia polygonifolia L. Seaside or Knotweed Spurge. (I. F. 

 f. 2307.) Pale green, glabrous. Branches radiately spreading, prostrate, forked, 

 5-20 cm. long; leaves opposite, oblong, linear-oblong or linear-lanceolate, 6-20 

 mm. long, fleshy, obtuse, often mucronulate, entire; involucres turbinate-campan- 

 ulate, less than 2 mm. long, with 4 columnar nearly naked glands shorter than the 

 lobes; capsule globose-ovoid. 3-4 mm. long, minutely wrinkled; seeds ovoid, some- 

 what flattened, ash-colored, very minutely pitted and spotted. In sand along the 

 Atlantic coast. N. H. to Fla., and on the shores of the Great Lakes. July-Sept. 



2 Euphorbia petaloidea Engelm. White-flowered Spurge. (I. F. f. 

 2308.) Pale green, glabrous. Stem erect, branched above, 1.5-6 dm. high; leaves 

 opposite, linear, oblong or linear-lanceolate, 1-2.5 cm. long, obtuse, usually flat, 

 straight, entire; involucres oblong-campanulate, 2 mm. long, bearing 4 wineglass- 

 shaped glands about as long as the lol>es. each subtended by a white ovate or orbic- 

 ular appendage; capsule globose-reniform, 2 mm. long; seeds oblong-ovoid, nearly 

 ash-colored, minutely pitted, nearly terete. Iowa to Wyo. and Tex. July-Sept. 



