Wein 
inmate ears ete 
seria %ia nana SAM SCH 
88 Braun and. Engelmann’s North American Equiseta. 
high ; but var. y. attains, according to the label in Prof. Short’s her-_ 
‘barat, a height of four feet and a half. The stems are simple, 
or éctasabally branched, with 20 to 24 carine, but I have col- 
lected specimens with from 18 to 27 carine. Generally they are 
perfectly smooth, but younger specimens and sometimes older 
ones also are somewhat rough, with rather persistent teeth, ap- 
proaching the small variety of the next species, but they can al- 
ways be distinguished from that by the sheaths being nearly 
twice as long, rarely with a black girdle at the base, more green, _ 
and by the medial carine: of the leaves not extending to the point. 
(In the small variety of EL. robustum, it is strongly marked and. 
very rough.) ‘The young sterile shoots with about 15 to 17 ca- 
rine are also more rough than the fertile stems, and resemble in 
that respect the branches, which have 7 to 10 leaves with persist- 
ent points. The sheaths, as has been stated, have generally only 
a narrow black limb, but some specimens have also, especially 
on the lower sheaths a black girdle at base; in one specimen I 
have seen the whole sheath black. The spikes are generally 
more obtuse than in E. hyemale. The var. y. has much the ap- 
pearance of E’. robustum, and it is equally large and stout, but is 
very distinct in all other respects. From the very fragmentary 
specimens seen by me, it seems impossible to distinguish it 
cifically from the Missouri plant. 5 
8. E. rosustum, A. Braun.—Stems very tall and stout, eral 
simple or slightly branching above; carine narrow, rough with 
one line of tubercles; grooves shiliags on each side with a sin- 
gle series of stomata ; vallecular air-cavities large, the carinal ones 
nearly none ; iesitunl cavity very large ; sheaths short, adpressed, 
with a Black girdle above the base, rarely with a black limb, con= 
sisting of about forty (in the hinehes eleven) leaves, 3- carinate. 
from the black girdle to the limb ; the points ovate-subulate, spha- 
celate, deciduous, leaving an ocean truncate margin. £. proce- 
rum, Bory ined., non Pollini. E.prealtum, Raf. ? Z 
6. manus, Bhan Fertile stems with 28 to 31 carine, 2 to 
3 feet high ; points of the leaves more persistent. 
-y- arrine, Engelm. Fertile stems simple, with 20 to 25 ca- 
rine, 1 to 2 feet high; teeth subulate-aristate, mostly persistent, 
black, rough, firially Seconog white. 
Hab. Islands of the Mississippi in Louisiana, (Bory de St. Vine 
cent.) Banks of Red River, (Dr. Hale, in herb. Short.) Banks” 
x 
