90 American Midland Naturalist Monograph No. 2 



6. Capsule shorter than or equalHng the perianth, greenish or pale 



brown; leaves flat. 



8. Auricles at the summit of the sheaths thin, scarious, hyaline, 



conspicuously extended beyond the point of insertion; fields, 



roadsides, open woods, very common. May-Sept. [/. tejiuis 



sensu Am. auth., non Willd.} /. macer S. F. Gray 



8. Auricles not conspicuously extended beyond the point of in- 

 sertion. 

 9. Sheaths and auricles membranous, hyaline; perianth erect, 



3-4 mm. long; sandy soil. May-Aug /. interior Wieg. 



9. Sheaths and auricles cartilaginous, yellowish; perianth spread- 

 ing, 4-5 mm. long; meadows, common. May-Aug 



/. dudleyt Wieg. 



4. Flowers in heads (glomerules) . 



10. Heads few (2-20) ; stamens not persistent; meadows or ditches, not 

 common. June-Sept /. marginatus Rostk. 



10. Heads numerous (20-100); stamens persistent, exserted; wet sandy 

 soil in the s. half of the state, not common. [/. aristtilatus sensu 



auth., non Michx.} /. b'lflorus Ell. 



3. Leaves terete, hollow, more or less septate. 

 1 1 . Stamens 6; seeds not caudate. 



12. Involucral leaf longer than the short-branched inflorescence; fila- 

 ments longer than the anthers. 

 13. Heads 7-10 mm. in diameter; flowers 3-4 mm. long, the petals 

 equalling or exceeding the sepals; wet ground, rare, n. III. 

 July-Aug /. nodosus L. 



13. Heads 1-1.5 cm. in diameter; flowers 4-5 mm. long, the petals 



much shorter than the sepals; ditches, common. July-Aug. 



/. torreyi Coville 



12. Involucral leaf much shorter than the long-branched inflorescence; 

 filaments about as long as the anthers. 



14. Branches of the inflorescence widely divergent; sepals acumi- 



nate; sandy shores, n.e. III. July-Aug /. articidatui L. 



14. Branches of the inflorescence erect or closely ascending; sepals 

 obtuse or mucronate; wet soil, n.e. 111. July-Aug. [/. alpinus 



var. instgnis Fries] /. richardsonianus Schult. 



11. Stamens 3. 



15. Seeds caudate. 



16. Perianth 3-4 mm. long, the segments acuminate; heads 5-50- 

 flowered; wet ground. Aug. -Oct /. canadensis J. Gay 



16. Perianth 2-2.5 mm. long, the segments obtuse; heads 3-5-flow- 



ered; wet ground. July-Sept 



/. brachycephalns (Engelm.) Buch. 



15. Seeds not caudate; perianth-segments acuminate. 



17. Capsule acuminate or subulate, longer than the perianth; heads 



2-30, each 15-40- flowered; perianth 2.5-3 mm. long; wet sandy 

 soil. July-Sept /. scirpoides Lam. 



