636 LXV. MARSILEACEiE. Azolla. 



growing in woods, Meriden, N. H. ! It bears a general resemblance to B, Lu- 

 naria of Europe, but is quite distinct from that species. Height 5 — 8'. Frond 

 9 — 20" long, ^ as wide ; segments 3 — 4 pairs, oblong, obtuse, erosely or incisely 

 dentate. Panicle subsimple, often larger than the fronds. Thecae 2-valved. Jl. 

 B. SIMPLEX. Hitchcock. 

 Sfipe bearing the frond above ; frond ternate, pinnatifid ; segments cune- 

 ate-obovate, incised, unequal; spike subcompound, unilateral, interrupted. — 

 Grows in dry, hilly pastures, Ms. ! Frond sheathed at base, with a lacerate 

 membrane, nearly simple, divided into 3 or more segments which are 1—2' 

 long, often much dissected. Stipe or scape 3 — 6' high. Thecae sessile. Jn. 



3. B. ViRGiNicuM. (B. gracile. P.) Rattlesnake Fern. 



Stipe with a single frond in the middle ; frcrtid twice and thrice pinnate, 

 the lowest pair of pinnae springing from the base ; idtimate segments obtuse, 

 somewhat 3-toothed ; spikes decompound ; pla?it subpilose. — A beautiful fern, 

 the largest of its genus, in low woods. Stipe or scape 1 — 2f high, bearing the 

 frond about hall-way up. This is apparently ternate, the lower pair of divi- 

 sions arising from the base. It is almost tripinnate, the ultimate segments 

 being decurrent and more or less confluent at base, with 3 — 5 cut serratures. 

 Panicle terminal, 3 — 6' long, reddish-tawny. June, July. 



4. B. FL-MARi6iDEs. WiUd. (B. obliquum. MiM.) 



Scape bearing the frond near the base ; frond in 3 bipinnatifid divisions ; 

 segments obliquely lanceolate, crenulate; spikes bipinnate. — Native of shady 

 woods and pastures. Frond almost radical, of a triangular outline, 3 — 5' long 

 and wide, of a stouter texture than the last, distinctly petiolate. Scape thick, 

 8 — 12' high, bearing a tawny, compound panicle 2 — 4' in length, composed of 

 numerous little 2-ranked spikes. Aug. 



/?. disscctum. Oakes. fB. dissectum. Willd.) Frond near the base of the 

 scape, more numerously aissected, almost tripinnatifid. 



Order CLXV. MARSILEACE^.— Pepperworts. 



plants stemless, creeping or floating. 



Leaves veiny, usually petiolate, often sessile and scale-like, sometimes destitute of a lamina. 

 Re productive organs oi two kinds; the one compound, the other simple, oval, radical bodies separate 

 from or mixed with the lirst, with many cells. 

 Genera 4, species 20? inhabiting ditches and inundated places in nearly all countries, but chiefly in 

 temperate latitudes. 



1. SALVINIA. Micheli. 



In honor of Salvini, professor of Greek at Florence. 



Stamens ? jointed hairs on the stalks of the ovary ; ovary nearly 

 sessile, among the roots, hairy, 1 — 5, opening at top ; fruit capsular, 

 covered with bristly hairs, containing reproductive bodies of two kinds, 

 one kind globular, the other oblong. 



5. NATANs. Willd. (Marsilea natans. Linn.) 



Leaves opposite, arranged in two rows upon the rhizoma, elliptical, entire, 

 subcordate at base, obtuse at apex, clothed with fascicles of hairs above ; ova- 

 ries ov fruit nearly globose, aggregated in subsessile clusters on the rhizoma, 

 submersed. — Floating, like a Lemna, in lakes and other still waters. West- 

 ern N. Y. and Can. Leaves nearly an inch long, of fine green. The plant is 

 quite rare. 



2. AZOLLA. Lam. 



Gr. (i^oi, to make dry, oXXt)//J, to kill ; as the plants speedily die when taken from the water. 



Stamens ? capillary : reproductive organs in pairs or numerous, of 

 two kinds, the one of two transverse cells, the upper containing seve- 

 ral angular, stalked bodies, the other stipitate, numerous, globose, 1- 

 celled, enclosed in an ovate, close involucre, and containing several 

 angular spores. 



