arvensé. 
[ 202 } 
CLASS XXI.—CRYPTOGAMIA. 
(FILICES.) 
385. EQUISETUM. Gen. pl. 1614. 
Floral receptacles peltate, many-angled, col- - 
lected into a spike. Indusium corniculate. 
Stamina 4. Style none. Seed 1.—WNutt. 
1. E. barren stems simply branched: branches 
somewhat rough, four-angled; fructification 
simple; sheaths cylindrical, incised-dentate ; 
teeth acute.— Willd. 
Icon. Schk. filic. t. 167. (Pursh.) 
Field Horse-tail. 
In wet fields near water courses; common. Perennial. 
May. 
sylvaticum. 2, EK. barren and fruit-bearing stems doubly- 
hyemale, 
branched; branches roughish, defiexed, four- 
angled; branchlets  sub-triquetrous.— Willd. 
enum. and Willd. 
Icon. Schk. filic. t. 166. Fl. Dan. 1182. 
Wood Horse-tail. 
In sandy woods bordering the Delaware, several miles be- 
low Kaighn’s point; rare. Perennial. April. 
3. E. stems simple, erect, very rough, bearing 
spikes at the top; sheaths discoloured, base 
and apex sphacelate; teeth aristated, entirely 
caducous.— Willd. 
Icon. Schk. filic. t. 172. 
Rough Horse-tail. Scouring Rush. Scour-grass. 
From two to three feet high. The cuticle of this species 
contains silex. Hence it is used in polishing pewter and 
