MAIISILEACEAE 



49 



5. B. obliquum and vars. x %. 



taironal, ternate and variouslj' decompound with stalked divisions, these ovate- 

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

 (il)li(iuely cordate or subcordate ; fertile seg- 

 ment erect, 2-4-pinnate. (i?. ternatitm, var. 

 ohliqmim Milde.) — Pastures and open woods, 

 N. B. to Ont, , Minn,, and south w. Fig. 6, a. 

 Polymorphous. The chief forms are : Yar. 

 ONEIDENSE (Gilbert) Waters. Fig. 5, h. Ulti- 

 mate divisions broadly oblong, rounded at the 

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

 to centr. N. Y. (Gilbert, Haberer), etc. Yar. 

 tenuif6lium (Underw.) Gilbert. Divisions 

 few, usually 9, thin ; otherwise much like the 

 typical form. — N. Y. (ace. to Gilbert); Mo. 

 (Bush), and southw. to the Gulf. Yar. ki.ox- 

 GATCM Gilbert & Haberer. Fig. 5, c. Divisions 

 lanceolate, elongated, acute. — Mass. to centr. 

 N. Y. and D. C. Yar. 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 

 W(wds, common, N. E., N. Y., and (?) n. Mich. Fig. 6. 

 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 sublunate. (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 Fekn.) Fronds 3-6 dm. tall, 

 ample ; 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. June, July. (Widely distr.) 



6. B. tern., v. intertn 



MARSILEACEAE 



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

 filiform or ^-parted long-petioled leaves ; the somewhat crustaceous several-celled 

 sporocarps borne on peduncles which rise from the rhizome near the leaf-stalks, 

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

 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, si»litting 

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



grat's manual — 4 



