436 FILICES. 



EQUISETUM, Linn. Horsetail. Scouring Rubh. 



The ancient name, from equus, horse, and tela, bristle. 



Spore-cases (sporangia, thecal) 6 or 7, adhering to the un- 

 der side of the angled shield-shaped scales of the spike, 1- 

 celled, opening, down the inner side and discharging the 

 numerous loose spores. To the base of these spores are 

 attached 4- thread-like and club-shaped elastic filaments 

 (elaters), which roll up closely around them when moist; 

 and uncoil when dry. — Stems simple, or with whorled 

 branches, and furnished at the joints with toothed sheaths. 



• Fertile stems simple, discolored, appearing be/ore the sterile one*. 



It E. ARVENSE, L. Field Horse-tail. 



Sterile sterna 10 to 15 inches high, smoothish, 12 to 14-furrowed, producing; 

 ascending sharply 4 (8 to 5)-angled long branches. with 4 herbaceous lanceolate, 

 pointed teeth : sheaths of the fertile stems 8 to 15. inchei high, remote, large and' 

 loose; spikes oblong, obtuse. 



Damp places, common. April, May.. 



• * Fertile stems at length branched, bearing the fructification uith th» branik*. 



2. E. sylvaticum, L. Wood Horse-tail. 



Sterile and fertile stems 12 to 18 inches high, about lC-furrowed, bearing; nu- 

 merous whorls of compound raeemed branohes ; sheaths loose, with 8 to IS rathe* 

 Munt membraneous teeth, which are more or less united ; tho^e of the branches* 

 bearing 4 or 5, of:the branchlets 3, lance-pointed divergent teeth ; tpikt oblong. 



Wet shady places. June, July. 



3. E..LIMOSUM, L. Smooth Swamp Horse-tail 



Stems tall, 2 to 3 feet high, smooth, slijhily 14 to 16-furrowed, usually produelng 

 upright simple branches after fructification^ sheaths apprcssed, rather short, with 

 dark-brown and acute rigid short teeth: spike oblong, scarcely an inch long 



Borders of swamps and ponds. June, July. 



• * * Stems simple or branched only at base ; ever green. 



4. Ei hyemale, L. Scouring Rush. Shave-grass. 



Stems stout and upright, 2 to 3 feet high, 14 to 26-furr.owed, the ridges reugk 

 with 2 rows of minute tubercles; sheaths close, whitish, with the top and bottom 

 black, with awl-shaped black teeth, which soon fall away, leaving a bluntly crenate 

 margin; spike ovoid, blackish.. 



Wet banks, common, well known for its use in scouring. June, July. 



5. E. variegatum, Schleicher. Variegated Horse-tail. 



Stems ascending, 6 to 12 inches long, simple from a branched and tufted base, * 

 tr ©-furrowed, the ridges rough, with 2 rows of tubercles wchich are separated by 

 a secondary furrow; sheaths enlarged upwards, green - variegated with black 

 above ; the teeth persistent, obtuse, tipped with a deciduous bristle; ipik$t ovoid, 

 blackish. 



Wet sandy piaees. 



Order 185. FILICES. —Ferns. 



Leafy plants, with the leaves (fronds) usually rising from prostrate or iubUrrmm* 

 rootstocks, mostly sepcrately rolled up (circulate) in the bud, and bearing en tM 

 reint of their leuer surface or along the margins, the simplt fruci\floatum t *>\%c\ 

 consists •fl-eelled spore-oases (sporangia), opening In various ways, and dUcharg. 

 log the numerous minute sporei, (fig. 2.) 



