108 PUBLIC HEALTH BULLETIN NO. 286 



9. Stamens as long as petals, the anthers exserted be- 8. J. scirpoides. 

 tween them. 



9. Stamens much shorter than petals, included 10. 



10. Leaf-blades flattened and usually with incom- 9. J. polycephalus. 



plete septa; capsule manifestly beaked. 



10. Leaf-blades only slightly compressed; septa 10. J. validus. 

 complete; capsule beakless. 



11. Capsule not more than two-thirds as long as perianth. 11. J. brachycarpus. 



11. Capsule equalling or exceeding the perianth 12. 



12. Seed 0.7-2.5 mm. long, the body tapering 13. 



at both ends into a white tail. 



12. Seed less than 0.55 mm. long with an abrupt 14. 

 usually dark colored tail. 



13. Capsule scarcely exceeding perianth; plant not rigid-. 12. /. canadensis. 



13. Capsule exceeding perianth by about half its length; 13. J. trigonocarpus. 

 plant rigid throughout. 



14. Capsule exceeding the perianth 15. 



14. Capsule about equalling the perianth 14. J . acuminatus. 



15. Capsule dark brown at maturity 15. J.elliottii. 



15. Capsule straw-colored at maturity 16. J. debilis. 



1. J. repens Michx. — Various provinces over all of our territory, 

 most common in the Coastal Plain, in very acid as well as nearly 

 neutral waters. It has often been found in association with Anoph- 

 eles quadrimaculatus. 



2. J. effusus L. Soft-rush — Perhaps the most frequent species 

 of the genus in our territory. Shows wide tolerance of acidity and 

 has been found in association with Anopheles quadrimaculatus. 



3. J. coriaceus Mackenzie — Like the preceding ranges over all of 

 our territory, but infrequent and usually confined to springy places. 



4. J. marginatus Rostk. — Various provinces over all of our territory 

 but noted most frequently near the coast. 



5. J. bifiorus Ell. — Ranges over all our territory. Collected in 

 very acid as well as almost neutral situations. 



6. J. ahortivus Chapm. — Coastal Plain, along margins of ponds, 

 middle Florida to South Carolina. 



7. J. megacephalus M. A. Curtis — Coastal Plain, Florida to Vir- 

 ginia, mostly in calcareous situations. 



8. J. scirpoides Lam. — Occurs over all of our Coastal Plain terri- 

 tory, fairly frequent and often in very acid situations. 



9. J. polycephalus Michx. — Ponds and swamps, Coastal Plain over 

 most of our range. 



10. J. validus Coville — Should occur only in the westernmost portion 

 of our Coastal Plain; however, the senior author has one collection 

 from South Florida. 



11. J. brachycarpus Engelm. — Various provinces, Georgia north- 

 ward and westward. Collected from neutral soil in west Tennessee. 



12. J. canadensis J. Gay — Various situations, range similar to the 

 preceding. 



