-6 7 - 



3a. Stem and foliage glabrous 4. 



3b. Stem and foliage more or less pubescent (stems prostrate or 

 ascending, 1 4 dm. long) 7. 



4a. Erect or ascending, usually without basal branches (2 4 

 dm. tall) Spurge, Euphorbia preslii. 



4b. Prostrate or spreading, branched from the base (stems 1 4 

 dm. long) 5. 



5a. Leaves entire; plants of the shores of the Great Lakes 



Spurge, Euphorbia polygonifolia, 



5b. Leaves serrulate 6. 



6a. Leaves broadly oblong or obovate; seeds obscurely wrinkled 



Spurge, Euphorbia serpyllifolia. 



6b. Leaves narrowly oblong; seeds with prominent transverse 

 ridges Spurge, Euphorbia glyptosperma. 



7a. Seeds black Spurge, Euphorbia hirsuta. 



7b. Seeds red 8. 



8a. Leaves oblong Spurge, Euphorbia maculate. 



8b. Leaves elliptical to obovate; involucre split down one side 



Spurge, Euphorbia humistrata. 



9a. Flowers subtended by conspicuous petal-like white appendages 

 (part of the involucre) (4 10 dm. tall; summer) 



Spurge, Euphorbia corollata, 

 9b. Flowers not subtended by petal-like appendages 10. 



lOa. Stem-leaves below the inflorescence serrulate (2 5 dm. 



high; summer) 11. 

 lOb. Stem-leaves below the inflorescence entire 13. 



lla. Upper leaves acute Spurge, Euphorbia platyphylla* 



lib. Upper leaves obtuse, rounded, or notched at the apex 12. 



12a. Leaves of the involucre broadly triangular-ovate, widest 



near the base Spurge, Euphorbia obtusata. 



12b. Leaves of the involucre broadly obovate to nearly circular, 



widest near or above the middle Spurge, Euphorbia helioscopia. 



13a. Stem-leaves narrowly linear, less than 3 mm. wide (2 4 dm. 

 high; late spring and summer) 



Cypress Spurge, Euphorbia cyparissias. 



13b. Stem-leaves narrowly oblong-spatulate, more than 5 mm. wide, 

 and more "than 3 times as long as wide (2 6 dm. high; sum- 

 mer) 14. 



13c. Stem-leaves obovate to nearly circular, not more than twice 

 as long as wide (1 4 dm. high) 15. 



14a. Leaves at base of umbel narrow, resembling those on the 

 stem Spurge, Euphorbia esula. 



14b. Leaves at base of umbel broad, resembling those of the 

 inflorescence Spurge, Euphorbia lucida. 



