ORDER 158. EQUISETACE.E. 



415 



branchlets crowded, short, 2" wide ; leaves crowded, oblong, entire, obtuse, the 

 smaller ones with an 'uncinate (reflexed) slender point. 



7 S. SERPENS. Stems prostrate, with hair-like rootlets, 2-3-pinnate ; branchlets short and 



crowded, 1" wide ; Ivs. crowded, round-ovate, cordate, obtuse, entire, the smaller acute. 



8 S. DELICATISSIMA. Sts. creeping, 5 8', rooting, filiform, loosely 2-3-pinnate, 1" wide ; 



leaves ovate, obtuse, ciliate, not crowded, the middle ones scarcely smaller, acute. 



9 S. CAULESCENS. Glabrous, suberect, 1218', 3-4-pinnately branched, fern-like, and lan- 



ceolate in outline ; brauchlets close, 1 \" wide ; leaves close, ovate, entire, very acute, 

 the points turned upward ; smaller leaves mucronate ; stem straw-colored. 



10 S. \VILLDENOVII. Like the last as to stems and branches, but they are finely pubes- 

 cent, and the leaves are less crowded, ovate, and obtuse. 6 12', ovate in outline. 



1 1 S. ERYTHROPUS. Stems red, with scattered, appressed leaves ; frond wide-spread, 

 somewhat palmate, with crowded branchlets and leaves, branchlets \\" wide ; leaves 

 ovate-oblong, oblique, obtuse, ciliate, the smaller with long straight points. 



1 2 S. cusriDATA. Stem or frond 36', densely and somewhat dichotoinonsly branched ; 

 branchlets 1" wide ; leaves closely imbricated, all nearly alike, elliptical, ciliate, 

 bristle-pointed, with the point inclined upward. A variety (perhaps the fertile stems) 

 are lanceolate in outline, 2-3-pinnately branched. 



1 3 S. LEPIDOPHYLLA, Resurrection Moss, is a roundish ball when dry. In a cup of water 

 it goon expands into a dense circle of dark-green, densely 2-3-pinnate fronds, with 

 innumerable oval, obtuse, entire leaves. From Lower California. 



3. PSILOTUM, R. Br. Sporangia sessile, 3-celled, imperfectly 3-valved 

 by terminal chinks, filled witti farinaceous spores. Stem fork-branched, 

 with alternate, minute leaves, as if leafless. 



P. triq uctrum Swtz. Stem erect, 8 1(K, many times forked, and, with the branches, 

 3-angled ; leaves remote, f" ; fruit 3-lobed, sessile along the branches. E. Fla 



ORDER CLVIII. EQUISETACE.E. HORSETAILS. 



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

 sulcate, jointed, fistular between, and separable at, the joints. Sheaths 

 dentate, crowning each iuternode. Fructification a dense, oblong-cylin- 

 dric, terminal, and cone-like spike, composed of 6 sided, peltate scales, 

 arranged spirally, bearing beneath 4 7 spore-cases, which open laterally. 

 Spores globular, each with 4 elaters attached, involving them spirally, or 

 open when discharged. (Sec Figures.) 



EQUISETUM, L. SCOUIUNG 

 Rusn. Character the same as 

 that of the order. The sheaths 

 may be regarded as a whorl of 

 united Ivs. The cuticle abounds 

 in silex. 



555, Equisetum arvense. 556, E. sylvati- 

 cura. 557, Section of the spike, enlarged. 558, 

 A peltate scale with 7 sporanges beneath (or 

 one compound sporange), magnified. 559, A 

 spore with its elaters highly magniQed. 555^3 



Species fruiting in Spring and decaying before the following Winter. . .(a) 

 Species fruiting in Summer and lasting through the following Winter.. .(l>) 



