Order ]59.— EQUISETAOEjE. 



813 



tary, quadrangular. — A very small species, creeping on rooks, moss-like. Stem a 

 few inches in length, with numerous branches, which are J — 1' long, clothed with 

 grayish-green leaves. Spike J' long, 4-rowed, seemmg a mere continuation of the 

 branch. JL (S. rupestre L.)' 



2 S. selaginoides Gray. St. filiform, creeping; branches nearly erect, the flow- 

 ering ones simple ; Ivs. scattered, lanceolate, a little spreading, cUiaie-dcniiculaie ; 

 spike solitary, leafy. — In moist woods, N. States and Can. Spikes yellowish- 

 green, about j" long, the bracts foliaceous and twice larger than the true leaves, 

 which are about a line in length. Branches 3 — 6' high, the sterile ones much 

 divided. Jl. (L. selag. L. S. spinosa Beauv.) 



3 S. ^pu3 Spring. St. branching, prostrate and rooting near the base ; Ivs. or- 

 bicular-ovate, acute, membranaceous, alternate, amplexicaul, in 2 rows, with 

 minute, acuminate, superficial ones in a third row on the upper side ; spikes sub- 

 solitary. — A small, creeping, moss-like species, in wet, rocky shades, Can. to Ga., 

 not common. Stem 2 — 5' inches long, filiform. Leaves less than a line in length. 

 Spikes leafy, scarcely distinguishable from the branches. July, Aug. (L. apo- 

 dum L.) 



4 S. ornithopodioides Spr. BiED-OLiw Moss. Lvs. semicordate, ovato, 

 obtusish, entire, in 4 rows, the lateral spreading, distant below, crowded above, 

 the superficial much smaller, appressed ; spikes latefal, axillary, sessile ; stems and 

 branches prostrate. — Greenhouse and gardens. A pretty moss-like creeper, with 

 light green foliage. | Bur. 



3. PSILOTUffl, E. Br. (Gr. il^iXog, naked.) Sporangia sessile, 3- 

 celled, imperfectly 3-valved by terminal chinks, filled with farinaceous 

 spores. — Stem fork-branched, with alternate, minute leaves, as if leafless. 

 (Bevnhavdia, Willd.) 



P. triquetrum Swtz. Stem erect, many times forked, and branches three-angled, 

 8 to 10' high; lvs. remote, subulate, less than 1'' long, and the 3-lobed fruit ses- 

 sile along the branches. — Rooky cliffs, on the sea-coast of B. Ha. (Michx. in 

 herb. Baohman.) 



Ordeb CLIX. EQUISETACEJE. Horsetails. 



Plants leafless, simple stems, or with wborled branches. Stems striate-sulcate, 

 jointed, fistular between, and separable at, the joints. Sheaths dentate, crowning 

 each iuternode. Fructification a dense, oblong-eylindric, terminal and cone-like 

 spike, composed of 6-sided, peltate-scales arranged spirally, bearing beneath 4 to 1 

 spore-cases which open laterally. Spores globular, each with 4 elaiers attached, 

 involving them spirally, or open when discharged. (See Figures.), 



An Ovder consisUng at present of a single gentis, crowing in wet grounds, on river banks, and 

 borders of woods, throughout most conntrics. Tho Equisetaceae abound in the fossil remains of 

 coal measures with other Cryptogamia, as Lycopodiaoeai and Tilloes, indicating that these 

 plants were once of gigantic dimensions, 

 and formed a large part of the original flora 

 of our globe. /Species about 10. 



Propertie/i.—^he.y abound in silex, and 

 hence are used by cabinet-makers, comb- 

 makers, &c., in polishing their work. 



EQUISETUM, L. Scouring 

 Rush. (Lat. eqiius, ahorse, seta, 

 hair.) Character the same as that 

 of the order. — The sheaths may 

 be regarded as a whorl of united T34 

 leaves. The ridges of tho stem 



„,"« +„"k„„ „^A tlin rrrnntrna TS4, Equisetum arvense. 785, E, sylvaticum. 736, 



are air-tubes, and the grooves g^^^.'^'J^ j^^^pj^^,.„,^^g^,,'^3jJ'^ p^u^^^ ^^j- 



alone are pierced with the sto- with 7 sporanges beneatli (or one compound epo- 

 ^ range), roagnifietl. 738, A spore with its elators, 



mata. highly magnified. 



