462 ACOTYLEDONOUS PLANTS. 



HAB. Low grounds. Can. to Car. July. U- Stem 8 12 

 inches long, nearly erect, simple or bifid, dark green. Learc* 

 longer than in any of the preceding. Fruit axillary, sessile, 

 about an inch from the top of the stem, semicircular. The 

 stem often bears bulbs instead of capsules. 



13. L. selago Linn. : stem erect, fastigiate, dichotomously branch- 

 ed; leaves scattered, linear-lanceolate, pungent, entire, imbricate, 

 rigid ; fruit axillary and L. recurvum Willd. 



HAB. Highest summits of the White Hills, N. H. Big. Arctic 

 Amer. H.Stem 3 8 inches high, rigid, with the branches 

 of the same thickness from top to base. Leaves in about 8 rows, 

 spreading, shining. 



2. ISOETES. LAtn. 



Capsule membranaceous, not opening, immersed at the 

 base of the frond, one-ceiled. Seeds angular, attached to 

 numerous filiform receptacles. 



/. lacustris Linn. : leaves subulate, flat, somewhat terete, fleshy, di- 

 lated and imbricate at base. 



HAS. Bottoms of rivers, near Oswego Falls, N. Y. Pnrsh. 

 Penn. Nutt. <$ ScJuo. "U.Root broad and fistulous, with sim- 

 ple fibres. Fronds 2 5 inches long, dilated and imbricate at 

 base, all radical, flat above, convex beneath. Fruit monoecious ; 

 sori cordate-oval, immersed in a corresponding cavity at the 

 base of the frond. 



OEDER CXL1H. MARSILEACE^. Drown. Lind. 



Fructification radical. Involucre subspherical, not open- 

 ing, coriaceous or membranaceous, 1 or many-celled. Aqua- 

 tics. 



1. SALVINIA. Mlchdi. 



Involucres 4 9, imbricate, connate, resembling an unilo- 

 cular capsule. Spara inserted upon a central receptacle. 



fif. natans Willd. ; leaves elliptic, subcordate, obtuse, with faciclei 

 of hairs above ; fruit subsessile, aggregated. Marsilea natans Linn. 

 HAB. Lakes and still waters. Can. and western part of N. Y. 

 Pursh. &. Leaves nearly an inch long, opposite, 2 ranked, 

 fine green. Fruit globular, in radical clusters, under water. 

 Floating on water like a Lemna. 



2. AZOLLA. Lamk. 



Monoecious. STERILE ovate, of two cells separating 

 transversely ; the upper containing several angular stalked 

 bodies. FERTILE on the some plant; capsules numerous, 



