412 ORDER 156. MARSILEACE^E. 



SUBKINGDOM, CRYPTOGAMIA, 



OR FLOWERLESS PLANTS. Vegetables destitute of true stamens 

 and pistils, gradually descending to a mere cellular structure, 

 with reproductive organs of 1 or 2 kinds, producing, instead of 

 seeds, minute, dust-like bodies (spores) having neither integu- 

 ments nor embryo. 



PROVINCE, ACROGENS. Flowerless plants, having a regular 

 stem or axis which grows by the extension of the apex only, 

 without increasing in diameter, generally with leaves, and 

 composed of cellular tissue and scalariform ducts. (Ferns, 

 Mosses, Club-mosses, Horsetails, &c.) 



ORDER CLVI. MARSILIACE^. PEPPKRWOUTS. 



Herbs creeping or floating, with the leaven petiolate or sessile, circinate in 

 vernation. Fruit (sporocarps) situated at the base of the leaves or leaf- 

 stalks, containing the capsulur spomnge* of one kind with 2 kinds of spores, 

 or of 2 kinds with the different spores separated. 



* Leaves compound, on slender petioles, with 4 leaflets. Sterna creeping MARSILIA. 1 



* Leaves simple, grass-like, riiilical. Stem a corm JSOKTES. 2 



* Leaves minute, lobed, imbricated. Stem filiform, floating free ....AZOLLA. 3 



1. MARSILIA, L. Sporocarps at the base of the leaf-stalks, of ono 

 kind, 2-celled, cells transversely many-celled, separating into two lobes at 

 maturity. Sporangia inserted on each horizontal partition, of 2 kinds, 

 some 1-spored, others oo-spored. U Stems creeping and rooting. Leaves 

 petiolate, apparently radical, of 4 wh&rled leaflets, resembling clover. 



1 M. q uaclrilolia L. Lftc. round-cuneiform, as broad as long, glabrous ; eporocarps 



oblong, smoothish, 1, 2, or 3 on each short peduncle, at* large as a peppercorn, y. Pet- 

 ioles 3 5' high. Margin of pond, Litchfteld, Conn. (Prof. Eaton). Leaven floating. 



2 JWf. vestita Hook & Grev. Lfts. cuueiform-obovate, longer than broad, glab. ; sporo- 



carps glob. -oval. 2^", hisp., 1 only on each short (3") peduncle, 2-toothedon back. S-W. 



3 M. unciiiata Brann. Lfts. cuneiform-obovate, hispid, petioles 1 2-' high ; sporo 



carp2", subsessile at the base of the petioles, clothed with rust-colored wool. Iowa. 



2. ISOETES, L. Qrii.i WORT. Sporocarps oval, 1-celled, of 2 kinds, 

 sessile in the axils of the radica, ,v=.. and adhering to them. Spores in the 

 outer sporangia larger, globular; in the inner minute, powdery. U? 

 Leaves linear, grass-like, clustered on the short corm. 



* Species growing under water, generally wholly submersed, in ponds, &c. . Nos. 1 3 



* Species growing in shallow water, or in damp grounds, emersed Nos. 4 7 



1 1. lacustrlsL. Lvs. 2 6', subulate, rigid, erect-spreading ; sporocarps round-ovate, 



unspotted, the larger spores with crested ridges. Varies with the leaven setaceous- 

 uubnlate and recurved, the sporocarps rarely a little spotted. N. 



