EQUISETACEAE 



63 



Branches simple, solid, 3- or 4-5-angled, their sheaths 

 3-toothed, their first internodes not exceeding the 

 stem-sheath; silex in flat spines arranged in threes. 2. E. pratense. 

 Branches compound, solid, the primary 4-5-angled, the 

 secondary 3-angled; silex in double rows of hooked 

 spinules. 3. E. sylvaticum. 



Stems all alike; spores maturing in summer; branches simple or 

 none. 

 Sheaths rather loose; branches usually long; stems bushy 

 below, attenuate upwards. 

 Central cavity of stem very small, spike long; branches 

 hollow, 4-7-angled, their sheaths mostly 5-toothed; 

 silex in cross-bands. 4. E. palustre. 



Central cavity of stem larger, the other air-cavities 

 usually present under both the ridges and grooves of 

 the stem; spike short, commonly with abortive 

 spores lacking elaters; branches simple, 3-5-angled, 

 hollow or solid. 5. E. littorale. 



Sheaths appressed, branches usually short; central cavity 

 of stem very large, cavities present under the ridges, lack- 

 ing under the grooves; branches hollow. 6. E. fluvialile. 

 Stems mostly perennial, evergreen; spikes tipped with a rigid point; 

 stomata in regular rows. 

 Stems 0.8-1.2 m. long, usually many-grooved, rarely with a few 

 branches; teeth of the leaves soon deciduous; silex in two 

 indistinct lines of tubercles. , 7. E. hyemale. 

 Stems very slender, 1.5-9 dm long, tufted, usually 5-10-grooved; 



central cavity small; teeth tipped with a deciduous bristle. 8. E. variegatum. 



1. E. arvense L. In sandy soil, along roadsides, etc.: Newf. and 



Greenl. to Alaska, south to Va. and Cal. Also in Eu. and 

 Asia. 



Scattered throughout the range. 



2. E. pratense Ehrh. In sandy places: N. S. and Rupert River 



to Minn, and Alaska, south to N. J. Iowa and Colo. Also 

 in Eu. and Asia. 



Conn. Rare; in the Housatonic Valley near Oxford and Newton. 

 N. Y. Perhaps near N. Y., but not definitely known. 

 N. J. Closter, Bergen Co., rare; Sparta, Sussex Co. 



A rare and scattered species, perhaps more widely distributed than 

 seems apparent. 



3. E. sylvaticum L. In moist sandy woods and thickets: Newf. 



and Greenl. to Alaska, south to Va. and Iowa. Also in Eu. 

 and Asia. 



Scattered in most parts of our range. 



