FILICES. (ferns.) 537 



7. E. robllStUltl, Braun. Stems 3° -6° high; the ridges narrow,rough 



with one line of tubercles ; sheaths short, with a black girdle above the base, rarely 

 with a black limb, and about 40 deciduous 3-kecled teeth with ovate-awl-shaped points. 

 — River-banks, Ohio to Illinois, and southward. — Too near the last ; and passes 

 by var. affine, Engelm. (a smaller plant, with 20-25 awl-pointed more per- 

 sistent teeth) into the next. 



8. E. hyeimile, L. (Scouring Rush. Shave-Grass.) Stems l£°- 

 3° high, the ridges roughened by 2 more or less distinct lines of tubercles ; sheaths 

 elongated, with a black girdle above the base, and a black limb, consisting of 

 about 20 (17-26) narrowly linear teeth, l-keeled at the base and with awl-shaped 

 deciduous points. — Wet banks ; common, especially northward. Used for scour- 

 ing. (Eu.) 



■*- ■»- Stems low and slender, growing in tufts : sheaths loose or enlarging upwards ; 

 the summits of their 4-keelcd ovate membranaceous and persistent teeth tipped with 

 a fragile awn or cusp. 



9. E. varicgfafUIll, Schleicher. Stems ascending (6'- 12' long), simple, 

 from a branched base, 5 — ^-grooved; the ridges rough with 2 rows of tubercles 

 which are separated by a secondary furrow ; sheaths green variegated with black 

 above ; the 5-9 teeth tipped with a deciduous bristle. — Shores or river-banks, 

 New Hampshire (Bellows Falls, Carey) to Wisconsin, and northward; rare. 

 (Eu.) 



10. E. scil'poidcs, Michx. Stems thread-like (4' - 8' high), bent or curved, 

 rough, 3 - Argrooved alternately with as many bristle-pointed teeth, and with the 

 same number of intermediate furrows of equal width ; sheaths variegated with 

 black ; central air-cavity wanting. — Wooded hill-sides, New England to Penn- 

 sylvania, Michigan, and northward. (Eu.) 



Order 136. FILICES. (Ferns.) 



Leafy plants, with the leaves (fronds) usually raised on a stalk or petiole 

 (called the stipe), rising from a root or mostly from prostrate or subterranean 

 rootstocks. separately rolled up (circinate) in the bud (except in Suborder 

 III.), and bearing, on the veins of their lower surface or along the margins, the 

 simple fructification, icldcli consists of 1-celled spore-cases (sporangia), open- 

 ing in various ways, and discharging the numerous minute spores. (An- 

 theridia and pistillidia formed on the seedling plantlet !) — Comprises three 

 very distinct Suborders, which now are by many received as separate 

 families : — 



Suborder I. POLYPODINE^E. The True Ferns. 



Sporangia collected in dots, lines, or variously shaped clusters (sori or 

 fruit-dots) on the back or margins of the frond or its divisions, stalked, 

 cellular-reticulated, the stalk running into a vertical incomplete ring, which 

 by straightening at maturity ruptures the sporangium transversely on the 

 inner side, discharging the spores. Fruit-dots often covered (at least when 



