Scirpus 



Cyperaceae 



195 



Jan. 



Feb. 



Mar. 



Apr. 



May 



June 



July 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Mfles 



o ^5o 

 Map 372 



SciYpus acutus Muhl. 



Miles 



5 — 58 



Map 373 



Scirpus fluvi'atilis (Torr.) Gray 



similar to those in which the species is found. This variety is difficult to 

 separate from Scirpus debilis. In fact, they are united in Britton and 

 Brown, Illustrated Flora, ed. 2. The shape of the stem seems to be the 

 only constant character. The divaricating bract of Scirpus debilis is 

 very characteristic but it seems that all plants do not have a divaricating 

 bract. The shape of the achene can not be relied upon since on the same 

 plant one can find plano-convex as well as biconvex achenes. 

 Maine and Mass. to 111. 



4. Scirpus americanus Pers. Map 369. Frequent on the sandy shores 

 of lakes and on gravelly bars in streams. 



Throughout temperate N. A. ; also found in S. A. and Eu. 



5. Scirpus Torreyi Olney. Map 370. Very local in a few swamps of the 

 northwestern part of the state. 



Maine to Man., southw. to R. I. and Minn. 



6. Scirpus validus Vahl. Map 371. This species grows in sandy or 

 mucky soil in shallow water (usually 1-4 feet deep) in lakes and along 

 streams. It is usually found in every lake of the state and when a lake 

 begins to dry up it usually is the first species to occupy the area. 



Throughout temperate N. A.; also found in W. I. 



7. Scirpus acutus Muhl. (Scirpus occidentalis (Wats.) Chase.) Map 

 372. Rather frequent in the lake area in habitats similar to those of the 

 preceding species. 



Newf. to B. C, southw. to Mass., cent. N. Y., Mo., Ariz., and Calif. 



8. Scirpus fluviatilis (Torr.) Gray. Map 373. Infrequent in the lake 

 area and in the Lower Wabash Valley. It is usually found in wet places 

 about lakes, along streams, and in ditches and ponds. I have seen about 

 five acres of it in Knox County on the west side of Swan Pond. 



N. B. to the region of the Great Lakes and Minn., southw. to D. C, and 

 Kans. 



