538 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



31. Leaves rarely linear, inequilateral at base; herbage sometimes pubes- 

 cent; plants annual or perennial, often prostrate (35). 

 35. Capsules more than 3 mm. long (36). 



36. Capsules about 4 mm. long; seeds nearly flat on the inner face, 

 rounded on the outer; leaves entire, up to 1 cm. long. 



18. E. PLATYSPERMA. 



36. Capsules 3.1 to 3.3 mm. long; seeds quadrangular; leaves serrulate 



at least at the apex, 1 to 4 cm. long 22. E. trachysperma. 



35. Capsules shorter than 3 mm. (37). 



37. Stipules united into a glabrous, membranaceous scale; nodes often 



rooting; leaves entire; herbage glabrous; seeds smooth (38). 

 38. Plant perennial, common; staminate flowers 12 or more. 



27. E. ALBOMARGINATA. 



38. Plant annual, rare; staminate flowers 5 to 10. __ 28 E. serpens. 

 37. Stipules not united into a glabrous, membranaceous scale; nodes 



not rooting; leaves sometimes serrulate; herbage sometimes 

 pubescent; seeds often wrinkled or ridged (39). 



39. Capsules 2 mm. long or longer (40). 



40. Leaves (the longer ones) considerably more than 15 mm. long. 



25. E. HYSSOPIFOLIA. 



40. Leaves not more than 15 mm. long, mostly shorter (41). 



41. Plants pilose; leaves serrulate 45. E. serrula. 



41. Plants entirely glabrous; leaves entire (42). 



42. Seeds ovoid or obscurely angled; glands circular or 

 nearly so, the appendages absent: Var. arenicola. 



19. E. OCELLATA. 



42. Seeds quadrangular; glands transversely oblong, the 



appendages present 29. E. fendleri. 



39. Capsules shorter than 2 mm. (43). 



43. Cyathia in dense terminal glomerules, a few also sometimes 

 solitary in the upper axils; plant perennial but flowering 



the first year 23. E. capitellata. 



43. Cyathia solitary in the axils and at the tips of the branches 



(44). 



44. Seeds with definite regular transverse ridges, these usually 



passing through the angles (45). 



45. Plants erect; leaves mostly 15 mm. or longer; seeds with 



shallow concave depressions separated by low narrow 



ridges 25. E. hyssopifolia. 



45. Plants mostly prostrate; leaves rarely up to 15 mm. 



long; seeds with rounded transverse ridges as wide as 



or wider than the valleys between (46). 



46. Seeds radially ovate; capsule widest below the middle; 



herbage always glabrous. _ 38. E. glyptosperma. 



46. Seeds radially oblong-ovate to oblong; capsule widest 



at the middle; herbage (at least the stems) often 



pubescent 39. E. abramsiana. 



44. Seeds smooth to faintly or even strongly wrinkled but never 

 with definite transverse ridges (47). 

 47. Leaves always entire; stems wingless (48). 



48. Plant perennial but flowering the first year; glands 

 transversely elongate, the appendages present but 

 often narrow 30. E. polycarpa. 



48. Plant annual; glands circular or nearly so, the ap- 



pendages absent 40. E. micromera. 



47. Leaves mostly serrulate, if nearly entire then the stems 

 more or less winged (49) . 



49. Herbage more or less pubescent; leaves often wider 



below the middle and tapering to the apex; seeds 

 reticulately wrinkled to nearly smooth, the testa 

 dark gray under the whitish outer coat. 



26. E. VERMICULATA. 



49. Herbage wholly glabrous; leaves widest at or above 

 the middle; seeds more or less wrinkled but never 

 reticulately so, the testa tan to brown under the 

 whitish outer coat 37. E. serpyllifolia. 



