6 SELAGINELLACEAE. 



11. EQUISETUM. Horsetail. 



Perennial plants with extensively creeping rootstocks; stems 



simple or with whorled branches, furrowed lengthwise, hollow; 



rangia adhering on the under side of the shield-shaped scales 



of th<' spike, one-celled, opening down the inner side; spores of 



<,iic kind, with elaters. 



mi annual, <>f two kinds, the pale brown fertile ones appear- 

 ing in -^prinu before the herbaceous sterile ones; spikes not 

 ..pi.ul.it.-. , . . u . .. E - a ™ nse - 



Stem- perennial, all alike, evergreen; spikes tipped with a rigid 



Ridges of the stem somewhat roughened with tubercles. -E. hyemale. 

 Ridges of the Mem nearly smooth. E. laevigatum. 



Equisetum arvense L. Aerial stems annual, of two kinds; the fertile 

 pale-brown and shortdived, appearing in early spring before the sterile; 

 fertile >t<ms 10-20 cm. tall, simple, terete, bearing about four loose scanous 

 distant Bheaths, these whitish with about 12 brownish acuminate teeth; 

 ilc stems pale green, 10-40 cm. tall, marked with 6-19 furrows, with numer- 

 ous whorls of mostly Mmple, solid branches, these 4-angled or rarely 3-angled; 

 ny of the main stem small; spike 2-3 cm. long. Common in moist places. 



Equisetum hyemale robustum (A. Br.) A. A. Eaton. Scouring rush. 

 \, rial stems evergreen, all alike, 40-120 cm. tall, 5-20 mm. thick, marked with 

 20-3<> furrow-; ridges roughened usually with a single series of transverse 

 siliceous tubercles; sheath short, commonly marked with a black girdle at the 

 base and another at the base of the early-falling teeth; spike nearly sessile in 

 the uppermost sheath, 2-3 cm. long, tipped with a rigid point. 



Common in moist places. The stems are usually simple but under certain 

 conditions branches may be produced. 



Equisetum laevigatum A. Braun. Aerial stems evergreen, pale, mostly 

 simple, 40 90 cm. tall, marked with 14-30 furrows, the ridges nearly smooth; 



ii sheath marked with a black girdle at the base of the deciduous white- 

 margined teeth, and sometimes with another at its base; wall of the stem thin, 

 the cavity large; spikes 2-3 cm. long, borne on a stalk that usually exceeds 

 the uppermost sheath. 



( ommon in low ground, on railway embankments, etc. When the primary 



ms an- rut off near the base a large number of smaller stems are produced, 

 a form very similar to E. variegatum Schleich. 



Class III. LYCOPODINEAE. 



Plant moss-like; stems branched, solid, with numerous 

 i. ill leaves; -porangia solitary in the axils of the leaves or 



<<n their upper surface. 



Family 5. SELAGINELLACEAE. 



rem itrial, annual or perennial moss-like plants with branching 



nd scale-like leaves, which are many-ranked and uniform, 



four-ranked and of two kinds spreading in two planes; spo- 



