y 
: 
: 
i 
t 
t 
, 
7 
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X 
Braun and Engelmann’s North American Equiseta. 87 
these ranges consist of a single row of stomata; in many tropical 
species each range has two or more rows. ‘The spikes are mostly 
acute. 
* Heterophyadica. (It is questionable whether any species exists belonging 
to this section. E. myriocheton, Schlecht. and Cham. from Mexico, so far 
known only from sterile specimens, might possibly prove to have different 
and earlier fertile stems.) 
omophyadica. 
t Ranges of stomata consisting each of one row. 
7, E. vexvicatum, A. Braun.—Stems tall, erect, simple or some- 
what branching ; carinee convex, obtuse, smooth; grooves shal- 
low on each side, with a single series of stomata; vallecular air- 
cavities small, the carinal ones very minute ; central cavity large ; 
sheaths elongated, adpressed, with a black limb, consisting of 
about twenty two leaves with one carina at base and (by the ele- 
vation of the margins and depressions of the middle) two towards 
the point; points linear-subulate, sphacelate, caducous, leaving a 
truncate-dentate margin to the sheath; branches somewhat rough; 
sheaths with about eight indistinctly 3-carinate leaves ; points per- 
sistent, subulate, sphacelate with a narrow membranaceous margin. 
 scaprenium, Engelm.—Carine more elevated, somewhat 
rough with small tubercles; leaves above with two rather rough 
lateral carinee, convex in the middle; teeth subulate, black at the 
base, membranaceous on the margin and towards the point, 
mostly persistent. 
yj. ELatum, Aingelm.—Very 
leaves, the points linear-lanceolate, memb naceous, irregularly 
deciduous, leaving a ragged truncate-dentate black margin. 
Hab. On poor clayey soil, with Andropogon and other coarse 
grasses, at the foot of the rocky Mississippi hills, on the banks of 
the river, below St. Louis, (V. Riehl,) who discovered it 1840, 
(G. Engelmann) «. and $. 7. Near Newbern, North Carolina, 
(Loomis § Croom in herb. Short.) Mr. Curtis informs me that 
this is probably the only species in that section. 
‘In size and manner of growth this new species is closely allied 
to El. hyemale, and the larger variety to EZ’. robustum ; but it is 
easily distinguished by its smoothness, its long green sheaths, with 
a narrow black limb, and its darker green color; in some of these 
respects it approaches to E. limosum, but differs by the deciduous 
teeth, the regularly disposed stomata, the structure of the stem, 
etc. It is generally one and a half to two, and even three feet 
tall; sheaths with about thirty 
late branace 
