ORDER 159. EQUISETACE^E. 



813 



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

 few inches in length, with numerous branches, which are \ 1' long-, clothed with 

 grayish-green leaves. Spike ' long, 4-rowed, seeming a mere continuation of tho 

 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, ciliate-dcnticulate ; 

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

 green, about f " 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. &pus Spring. St. branching, prostrate and rooting near tho 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 25' 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. BIRD-CLAW Moss. Lvs. semicordate, ovate, 

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

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

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

 light green foliage, f Eur. 



3. PSILOTUM, R. Br. (Gr. $iMs, 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. 

 (Berahardia, Willd.) 



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

 8 to 1 0' high ; Ivs. remote, subulate, less than 1'' long, and tho 3-lobed fruit ses- 

 sile along tho branches. Rocky cliffs, on the sea-coast of E. Fla. (Michx. in 

 herb. Bachman.) 



ORDER CLIX. EQUISETACE^E. HORSETAILS. 



Plants leafless, simplo stems, or with whorled branches. Stems striate-sulcato, 

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

 each internode. Fructification a dense, oblong-cylindric, terminal and cone-liko 

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

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

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



An Order consisting at present of a single genu*, growing in wet grounds, on river banks, and 

 borders of woods, throughout most countries. Tho Equisetaoeae abound in tho fossil remains of 

 coal measures with other Cryptogamia, as Lyoopodiaceae and Filices, indicating that theso 

 plants were once of gigantic dimensions, 



and formed a largo part of the original flora K. > ^ n-yrrjrr-*-* ^fc> 



of our globe. Species about 10. 



Properties. They abound in silex, and 

 hence are used by cabinet-makers, comb- 

 makers, &c., in polishing their work, 



EQUISETUM, L. SCOURING 

 RUSH. (Lat. equus, a horse, seta, 

 hair,) Character the same as that 

 of the order. The sheaths may 

 be regarded as a whorl of united 734 

 leaves. The ridges of the stem 



orrt nir tnKoc vnrl tho oroovps 734, Equisctnm arvense. 735, E, sylvaticum. 780, 



are air-tubes, ana 3 grooves Sccth ' m ^ f thospik<N enlarged . 737, A peltate scaio 



alone arc pierced With the Sto- with 7 sporanjres beneath (or one compound spo- 



range), magnified. 738, A spore with its elators, 



inata. 



highly magnified. 



