Species of Lycopodium of North America 149 



Leaves arranged so as to lie in nearly one plane ; stems pinnately branch- 

 ing, prostrate. * 7. Z. pinna turn. 

 Sporangia transversely compressed, reniform ; sporophylls entirely unlike the 



foliar leaves. 



Leafy stems short (2-15 cm.), prostrate, leaves lying nearly in one plane, 



none beneath. 8. Z. Carolinian urn. 



Stems with abundant erect or ascending leafy branches. 



Leaves equal, radially arranged (except on the terminal branches of no. 



11) in five or more rows. 

 Aerial portions dendroid. 



Strobiles few, stout, erect. 11. L. obscurum. 



Strobiles numerous, short, nodding. 12. Z. cernuum. 

 Aerial portions extensively trailing, with clustered branches. 

 Leaves in five rows ; stems and branches slender (2 mm. ). 



13. Z. Site /tense. 

 Leaves in more than five rows. 



Strobiles solitary, sessile. 9. Z. annotinm. 



Strobiles l-several on evident elongate peduncles. 



10. Z. elavatum. 



Leaves in four rows on flattened aerial dorsiventral stems. 



Branches convex on both sides ; leaves alike in all four rows. 



14. Z. sabinaefoliiwi. 

 Branches with under surface flat or concave. 



Strobiles pedunculate, peduncles usually forked twice. 

 Leaves of under row scarcely reduced ; terminal. 



15. Z. ehamaeeyparissiis. 

 Leaves of under row much reduced to a subulate tip ; 



terminal branches spreading, horizontally fan-shaped. 



16. Z. complanatnm. 

 Strobiles sessile upon stronger leafy branches ; leaves of the 



under row trowel-shaped. 17. Z. alpinum. 



I. L. Selago L. Sp. PL 1 102. 1753 



Prostrate portion of stem very short, abundantly rooting, soon 

 curving upward and dichotomously branching to form compact 

 tufts (4-17 cm. high) of vertically placed branches with dense 

 foliage : leaves more or less appressed, or at least upwardly directed, 

 triangular (1.5 x 4 mm.) to linear-acuminate (0.5 mm. x 5 mm.) 

 or aciculate (1 mm. x 8 mm.), broadest at the hollow base, gradu- 

 ally tapering to the acuminate apex, entire: sporophylls shorter 

 than the leaves, triangular : sporangia reniform : plant very fre- 

 quently gemmiparous. 



A boreal and arctic plant, showing a considerable degree of 

 variability. Alaskan material shows a range of variation in its 

 leaves which measure from 2x4 mm. to 1 x 8 mm., and this in the 

 same habitat, judging from a series of specimens collected by Thos. 



