MARSILEACEAE 



49 



5. B. obliquum and vars. 



tagonal, ternate and variously decompound with stalked divisions, these ovate- 

 oblong, acutish, usually two or three times as long as broad, crenate-serrulate, 

 obliquely cordate or subcordate ; fertile seg- 

 ment erect, 2-4-pinnate. (B. ternatum, var. 

 obliquum Milde.) Pastures and open woods, 

 N. B. to Ont., Minn., and south w. FIG. 5, a. 

 Polymorphous. The chief forms are : Var. 

 ONEIDENSE (Gilbert) Waters. FIG. 5, 6. Ulti- 

 mate divisions broadly oblong, rounded at the 

 apex, crenulate-serrulate. Vt. (Miss Gilman) 

 to centr. N. Y. (Gilbert, Haberer~), etc. Var. 

 TENUIFC>LIUM (Underw.) Gilbert. Divisions 

 few, usually 9, thin ; otherwise much like the 

 typical form. N. Y. (ace. to Gilbert}; Mo. 

 (Bush), and south w. to the Gulf. Var. ELON- 

 GATUM Gilbert & llaberer. FIG. 5, c. Divisions 

 lanceolate, elongated, acute. Mass, to centr. 

 N. Y. and D. C. Var. DISSECTUM (Spreng.) 

 Clute. FIG. 5, d. Divisions incisely many- 

 toothed. Often with the typical form in N. E., 

 N. Y., andO. 



6. B. ternatum (Thunb.) Sw., var. intermedium D. C. Eaton. Stout, 

 decidedly fleshy, loosely pubescent to subglabrous, 1.5-4 dm. high ; habit and 



fertile segment as in the preceding ; sterile segment becoming 

 large (sometimes 2 dm. broad), its ultimate divisions numer- 

 ous, ovate or obovate, commonly subcuneate or semicordate 

 at the base, crenulate and more or less lobed, usually obtuse 

 or rounded at the apex. (Including var. australe D. C. 

 , Eaton, as to Am. plant.) Sandy soil, pastures and open 



' ; ' - woods, common, N. E., N. Y., and (?) n. Mich. FIG. 6. 



\\x^ ^Passing insensibly into var. RUTAEFOLIUM (A. Br.) D. C. 

 *"~ Eaton. More slender, rarely over 1.7 dm. high; sterile 

 segment commonly about 5 cm. broad, its divisions few, 

 broadly ovate, the lowest sublimate. (B. Matricariae Spreng. ; 

 B. rutaceum Sw.) Nfd. to s. N. H., and n. Mich. (Eurasia.) 



2. OSMUNDOPTERIS Milde. Base of the stalk (contain- 

 ing the bud) open along one side ; sterile segment mem- 

 branaceous the cells of the epidermis flexuous. 



7. B. virginianum (L.) Sw. (RATTLESNAKE FERN.) Fronds 3-6 dm. tall, 

 >iple ; sterile segment sessile above the middle of the plant, broadly triangular, 



thin and membranaceous, ternate; the short-stalked primary divisions once or 

 twice pinnate, and then once or twice pinnatifid ; the oblong lobes cut-toothed 

 toward the apex ; veins forking from a midvein ; fertile part 2-3-pinnate. 

 Rich woods, common. Ju 



filifc 

 spon 



rime, July. (Widely distr.) 



MARSILEACEAE 



Perennial plants rooted in mud, having a slender creeping rhizome and either 

 liform or ^-parted long-petioled leaves ; the somewhat crustaceans several-celled 

 rocarps borne on peduncles ivhich rise from the rhizome near the leaf-stalks, 

 or are more or less consolidated with the latter, and contain both macrospores 

 and microspores. 



1. MARSILEA L. 



Submersed or emersed aquatic plants. Leaves 4-foliolate. Sporocarps with 2 

 teeth near the base, 2-celled vertically, with many transverse partitions, splitting 

 into 2 valves at maturity, and emitting an elastic cord or band of tissue, which 

 GRAY'S MANUAL, 4 



