26 22. Equisetura. 4. EQUISETACE^E. Pl.end.cr. 



3. Eguiseiuni arvense. Coriijleld horse tail. 



Barren stems simply branched, branches roughish, four- 

 sided; frui'fid stems simple; sheaths cylindrical, distant, 

 inciso-dentate ; teeth acute. 



E. arvense longioribus setis, Rati Syn. 1,30, 2; Park. 1202. 

 £. segetale and E. sylvaticum, Ger.em, 1114. 

 Equisetum arvense, Lin. S. P. 1516. 



In moist cornfields and meadows; perennial; March 

 and April. 



Barren stems, high, branched in all parts; sheaths small; 

 Iranches verticillate, spreading, angular; angles rathet 

 rough: Fertile stems earlier, 6 inches high; sheaths very 

 long ; spike lanceolate, long, large. 



^. elongatum. Branches very long. 



E. pratense, longsssimis setis, Rail Syn. 131, 8. 



4. Equisetum Jluviatile. River horsetail. 

 Barren stems simply branched; branches rather rough, 



numerous, eightsided; //-m////// stems simple; sheaths fun- 

 nelshape, rather close, lacero-dentate ; teelh bearded. 



E. majus, Rati Syn. 130, 1 ; Ger. em. 1113. 

 E. majus palustre, Park. 1209. 

 E. eburneum, Roth Germ. 111. 

 E, fiuviatile, Lin, S. P. 1517. 

 Great horsetail. 



Marshes and river banks ; perennial ; April. 



Barren stem 5 or 6 feet high, upright, branched; Iranches 

 numerous, verticillate, long, usually simple, rough when 

 viewed by a lens; fruitful stems very simple; sheaths short, 

 brown, edge manycut, bristly ; spike very large. 



5. Equisetum limosum. Mud horsetail. 

 Stalk naked, branched ; Iranches about twelve, fivesided, 



smooth ; spike terminal. 



E. nudum laevius nostras, Rail Syn. 131, 10. 

 E. fliiviatile, F;. i)fln. 1184. 

 E. limosum, Lin. S. P. 151T. 

 Smooth naked Iwrsctail. 



Marshes and watery places ; perennial ; June and July. 



Stems two feet high, very smooth ; branches few, erect, 

 smooth, very rarely verticillate ; spike large, brown, ovate ; 

 larren stems very simple, narrow at top. 



^. ramosum. Stem branched. 

 E. foliis nudum ramosum, Rati Syn. 132, 12. 



