654 EQUISETACE^E. (HORSETAIL FAMILY.) 



1. Annual-stemmed, not surviving the winter. (Stomata scattered.) 



* Fruiting in spring from soft and rather succulent pale or brownish fertile stems, the 



sterile stems or branches appearing later, herbaceous and very different. 

 *- Fertile stems remaining simple, soon perishing ; the sterile producing copious branches. 



1. E. Telmatdia, Ehrh. (GREAT HORSETAIL.) Stems stout (as thick 

 as the finger) ; the sheaths of the fertile ones (l'-l' long) enlarging upwards, 

 deeply 20 - 30-toothed ; sterile stem white, 20 - 30-furrowed ; its branches simple, 

 rough, usually 4-angled and again grooved on the angles. (E. ebiirneum, Roth., 

 Schreber, and Ed. 2. E. fluviatile, Smith.) Shore of the upper Great Lakes, 

 and northwestward: rare. April, May. Fertile stems 10' -15', the sterile 

 2 -5 high. (Eu.) 



2. E. arv&ise, L. (COMMON H.) Fertile stems (4' -10' high) with 

 loose and usually distant about 8-12-toothed sheaths; the sterile slender (at 

 length l-2 high), 10-14-furrowed, producing long and simple or sparingly 

 branched 4-angular branches ; their teeth 4, herbaceous, lanceolate. Moist, 

 especially gravelly soil : very common. March - May. Rootstocks occasionally 

 bearing copious little tubers like small peas (Illinois, S. A. Collier). The var. 

 SEROTINUM, Meyer, an accidental state, in which the sterile plant produces a 

 spike of fruit from its summit, is found in New Jersey by C. F. Austin. 



*- *- Fertile stems when older producing herbaceous 3-sided branches, and lasting 

 through the summer, except the naked top which perishes after fructification. 



3. E. pratense, Ehrh. Sterile and finally also the fertile stems producing 

 simple straight branches; sheaths of the stem with ovate-lanceolate short teeth, 

 those of the branches 3-toothed : stems more slender and the branches shorter 

 than in the last. (E. umbrosum, Willd. E. Drummdndii, Hook.) Michigan 

 (Cooley, $-c.), Wisconsin, and northward. April, May. (Eu.) 



4. E. sylvaticum, L. Sterile and fertile stems (about 12-furrowed) pro- 

 ducing compound racemed branches; sheaths loose, with 8-14 rather blunt teeth, 

 those of the branches bearing 4 or 5, of the branchlets 3, lance-pointed divergent 

 teeth. Wet shady places : common northward. May. (Eu.) 



* * Fruiting in summer ; the stems all of one kind, or the fertile contemporaneous with 



and like the sterile, equally herbaceous, producing mostly simple branches, or some- 

 times nearly naked. 



5. E. pallistre, L. Stems (10' - 18' high) slender, very deeply 5 - 9-grooved, 

 the grooves separated by narrow wing-like ridges, roughish, the lance-awl-shaped 

 teeth whitish-margined ; branches rather few in a whorl. Wet places, Niagara 

 River ( G. W. Clinton), Wisconsin ( C. F. Austin), and northward. June. (Eu.) 



6. E. limbsum, L. Stems (2 -3 high) slightly many-furrowed, smooth," 

 usually producing upright branches after fructification ; sheaths appressed, with 

 10-22 (commonly about 18) dark-brown and acute rigid short teeth. (E. uli- 

 ginosum, Muhl.) In shallow water : rather common. Air-cavities none under 

 the grooves, but small ones under the ridges. June, July. (Eu.) 



(E. LITTOR\LE, Kiihlewein, a species of N. Europe which stands between 

 No. 5 and No. 6, is said by Milde to grow in Canada, on the authority of a 

 specimen in herb. Hook., and may be looked for northward.) 



