Pet 
"eo 
3 es, and become similar to the sterile ones and persistent through 
«the season, (E. susvernatia, Subvernal Equiseta,) as is the case 
in dy slbiniticuts and &. pratense. 
EQUISETUM, Linn. 
$1. Equisera spemropora: stomata irregularly dispersed over 
the whole surface of the grooves. 
* Heterophyadica: fertile stems different from the sterile ones; the former 
early and discolored ; the latter later and herbaceous. 
t Ametabola (Vernal Equiseta): fertile stems simple, never herbaceous, de- 
ciduous before the full development of the sterile stems 
1. E. arvense, Linn.—Sterile stems grooved, smoothish; 
sheaths consisting of about eleven l-carinate leaves; carine 
with a very slight furrow on the back ; the commissural furrows 
between them slight; carine of the simple branches compressed, 
rough ; sheaths consisting of four 1-carinate leaves, with herbace- 
ous ovate-acuminate subsquarrose teeth. Fertile stems simple ; 
up to the apex, finally separate into short teeth. 
The sheaths of the fertile and sterile stems are composed (ac- 
cording to the size of the specimens) of from 7 to L5, but gener- 
‘gs ally 10 to 13 leaves ; the sheaths of the branches are mostly 4-, 
seldom 3- or 5- eoihed. The summit of the sterile stem is atten- 
3 uated, and like one of 5 branches.—We disti guish the follosr- 
ing varieties. fe 
8. NEMOROSUM 4 ae * Large, 12 to Dine high the 
branches with a pa branchlets. pratense, Roth and others, 
not Ehrh. In specimens from Missouri, the sheaths have 12 to 
15 teeth; the fertile stems are 12 to 15, and the sterile ones 15 
to 20 haber high: branches frequently 6 or 7 inches long. 
teeth: stems 4 to 6 inches high; the lowest branches with a few 
hlets. 
8. serotinum, Meyer, Chl. Hanov. The usually sterile her- 
baceous stems also with fructification —F. campestre, Schultz, 
prodr. fl. Starg. 
Hab. Europe, Northern Asia, North America, from Greenland 
to the Northern States and Virginia, (Pursh,) to Kentucky, 
et 
* iil. 
Pe y 
2 sip ) — 
Braun and Engelmann’s North American E'quiseta. fs3_) 
the sheaths consisting of 2-carinate leaves, which, at first connate 
y. pecumsens, Meyer, Chi. Hanov. Sterile stems branching 
from the base, procumbent. In Missouri, sheaths with 7 to 8 
(Short,) Missouri, (Engelmann, Riehl,) the Rocky Mountains, 
