"| 
on 
oe 
A 
Braun and Engelmann’s North American Equiseta. fes_} 
which, before the development.of branches, distinguish the fer- 
_ tile stem from #. arvense. E. sylvaticum as well as E’. arvense 
' have tubers on the creeping rhizoma, which Prof. Braun could 
- not find in #. eburneum ; the other species have certainly none. 
4. E. pratense, Hhrh.—Sterile (and finally also the fertile) 
stems with simple straight branches, both grooved; carine sca- 
brous, in one row; sheaths consisting of about 11 leaves, with 
very shallow carinal and deeper commissural furrows, teeth sca- 
rious, ovate-lanceolate, and all free; carinze of the branches slight- 
ly scabrous, much compressed ; urceolate sheaths consisting of 
three 1-carinate leaves with herbaceous erect very short and 
somewhat obtuse teeth.—H. umbrosum, Meyer, in Willd. £. 
Ehrharti, Meyer, Chl. Hanov. E. amphibolum, Retz. £. tri- 
quetrum, Bory. E. Drummondii, Hook. 
Hab. This species appears to inhabit extensively the northern 
countries of Europe and Asia; it is rare in Scotland, common in 
Scandinavia, in the North of Germany, in Russia and Siberia; 
also in the Alps and Pyrenees; in Arctic America and Greenland 
according to Sprengel. It is easily distinguished from the forego- 
ing, much more common, species by the shorter, never connate 
teeth of the sheaths of the stem, the 3-teethed sheaths of the 
branches, and the absence of branchlets. 
** Homophyadica, (Summer Equiseta): fertile and sterile stems similar, 
both herbaceous and contemporaneous; or all the stems fertile. (All the 
known species belonging to this section have annual : ems, not persistent i 
winter.) — me pee eee a: ae ' 
5, E. PALusTRE, in <item generally with simple verticil- 
late branches, deeply grooved, somewhat scabrous; vallecular air 
cavities large, the carinal ones very small; sheaths loose, consist- 
ing of about 8 leaves separated by shallow commissural furrows 
and above with carinal ones; teeth lanceolate, acute, dark ferru- 
ginous, with broad membranaceous margins ; branches smilar to 
the stem, with acuminate adpressed somewhat sphacelate teeth 
of the mostly 5-leaved sheaths. . pratense, Reichenb., not 
Ehrh. nor Roth. c te 
8. simpxicissimum. Stems without branches. 
y. Potystacuyum. Branches elongated, bearing heads. 
Hab. Europe, North America, Arctic America to Virginia, 
(Beck's Botany.)—Sheaths of the stem with 6 to 10, mostly 7 
to 9 teeth. A very polymorphous species. Nearly related to this 
ull 
