136 OUR NATIVE FERNS AND THEIR ALLIES. 



bright green, those of the under row reduced to spreading 

 cuspidate apices; peduncles usually forlcing twice, the sec- 

 ond forlcing i" — 2" from the first ; strobiles 7"— 12" long ; spores 

 ripening late in August or in September. Canada to Maryland 

 and northwestward to Washington and Alaska. 



16. L. chamsecyparissus A. Br. Rhizomes creeping 

 below the surface; primary shoots weak, often becoming de- 

 cumbent, the axis repeatedly forking, regularly producing in- 

 novations the second season ; leaves in four rows, all much 

 alike, those of the lateral rows somewhat incurved beneath, 

 glaucous green ; peduncles usually twice forked, the second 

 forking 4" — 9' from the first, spreading and curving upward ; 

 strobiles 2, 3, or usually 4, 10" — 14". long ; spores ripening early 

 in August. Maine to Georgia, Minnesota. 



17. L. alpinum L. Prostrate stems 8' — 20', on or near the 

 surface; aerial stems numerous and branching several times to 

 form dense clumps 2' — 3' of markedly dorsiventral branches 

 with glaucous foliage ; occasional strobile-bearing branches 

 (peduncles) thicker, terete, and usually projecting above the 

 general mass ; leaves of the peduncles subulate, those of the 

 purely vegetative branches trimorphic, those of the upper row 

 narrowly ovate, acute, those of the lateral rows thick, with one 

 nerve asymmetrically placed, truncate, acute, falcate, curved 

 toward the under side, those of the under row trowel-shaped ; 

 strobiles sessile, 5" — lo'' long, with ovate acute sporophylls. ; 

 sporangia reniform. British Columbia, Alaska, Greenland. 



XI. PSILOTUM R. Br. 



Perennial plants, terrestrial or growing on trees. Stems 

 dichotomously branched with minute alternate leaves, or ap- 

 parently leafless. Sporangia sessile, 3-celled, opening at the 

 apex into 2-3 valves. Spores farinaceous, oval, or elongate- 

 reniform. Name from Gr. ipiXoi, naked, alluding to the 

 abortive leaves. Contains four species, mostly tropical. 



I. p. nudum (L.) Griseb. Stems erect, 8' — 10' high, tri- 

 quetrous at base, many times forked at apex; ultimate di- 

 visions triquetrous-winged ; leaves remote, awl-shaped, less 

 than l"long; sporangia in spikes. (P. Floridianunt Michx., 

 P. triquetrum Swz., Lycopodium nudum L.) South Florida; 

 Bluffton, South Carolina (Mellichamp). 



