134 OUR NATIVE FERNS AND THEIR ALLIES. 



linear-lanceolate and twisted especially above so as to lie in a 

 vertical plane, acute, mucronate, on the lower branches in 8 

 rows, on the terminal in 6 rows ; strobiles sessile ; sporophylls 

 broadly ovate, papery, and erose-margined, acuminate with a 

 subulate apex ; sporangia reniform. (Z. dendroideuvi Michx.) 

 North Carolina to Canada, Minnesota, Montana, and Alaska. 



10. L. cernuum L. Stems 8' — 14' long, procumbent or 

 arching, with clustered roots at points of contact with the 

 ground, branching often in different planes, the terminal 

 branchlets often strobile-bearing and nodding ; leaves cylin- 

 dric, slender, subulate, spreading, and upwardly curving ; 

 strobiles sessile, 2" — 3" long, nodding, with small sporophylls 

 ovate-acuminate, thin,_with deeply fringed margins; sporangia 

 minute, spherical, transversely compressed. Mississippi, Ala- 

 bama, and Florida near the coast. 



\ II Aerial portions trailing with clustered branches. 

 A. Leaves in 6 — 8 rows, 



11. L. annotinum L. Prostrate stems a yard or more 

 long, extensively creeping along the surface, very rarely pin- 

 nately branching, stiff, rooting, leafy, with frequent aerial 

 branches 6' — 10' tall, which fork i — 3 times or not at all, pro- 

 ducing slender erect branches, which are usually strobile-bear- 

 ing; leaves in 8 rows, uniform in shape throughout the plant, 

 longest in the aerial parts, where they spread horizontally, or 

 are finally somewhat reflexed with upwardly curving apices, 

 lanceolate to linear-lanceolate, broadest at or above the middle, 

 serrulate, acute, or pungent ; strobiles sessile upon the leafy 

 vertical branches, thick, with broadly ovate sporophylls, the 

 latter with erose margins and subulate tips. The so-called var. 

 pungens has stiffer, shorter, more erect leaves. Massachusetts 

 and Pennsylvania, northward and westward to Colorado, Idaho, 

 Washington, and Alaska. 



12. L. clavatum L. (RuNNlNG-PlNE.) Prostrate stems 

 3° — 6° long, creeping extensively along the surface of the 

 ground, very leafy, sparingly rooting, branching horizontally, 

 with frequent aerial stems which are immediately ascending or 

 at first prostrate, then ascending, producing pinnate branches 

 of the second and third order, lax, some of them produc- 



