1921] Evans, — Notes on New England Hepaticae, — XVI 283 



at the base. The ventral lobe is plane to slightly convex; it has much 

 the same shape as the dorsal lobe but is somewhat larger, measuring 

 (in well-developed leaves) 1.2-1.5 mm. in length by 1-1.2 mm. in 

 width. The apex and margin are like those of the dorsal lobes but the 

 decurrence tends to be somewhat more marked. The median leaf 

 cells of the lobes measure about 20 X 1o;jl and are marked by large 

 pigmented trigones, usually with bulging sides and often giving the 

 cell-cavities a more or less stellate outline. The cuticle is smooth or 

 nearly so. The gemmae, first described and figured by Mliller, are 

 oval bodies, mostly 15-20;jl in length and 10-15ix in width. They 

 occur in dense claret-colored masses and are mostly two-celled, 

 although one-celled gemmae also occur. The lobes of the male 

 bracts are almost equal, and the mouth of the perianth is sparingly 

 toothed; otherwise the sexual plants yield no additional characters of 

 importance. 



Jorgensen compared his species with the European S. crassirctis 

 Bryhn, but later writers have shown that its true relationship is 

 with S. irrigua (Nees) Dumort. and S. paludicola Loeske & K. Mull. 

 In both of these species trigones are a characteristic feature of the 

 leaf-cells but are much less conspicuous than in S. hyperborea. The 

 species are further distinguished by their yellowish green color, pale 

 gemmae and abruptly pointed leaves, although in S. irrigua at least 

 rounded leaves also are of frequent occurrence. The keels of the 

 leaves in S. irrigua are much like those of S. hyperborea, but those of 

 S. paludicola are normally wingless and strongly arched. 



Although the distinctions emphasized will usually serve to separate 

 these three species without difficulty, certain European forms have 

 been described which seem to connect S. hyperborea with its allies. 

 The most important of these are the following: S. remota Kaalaas 

 (1898), S. irrigua var. alpina Bryhn (1902), and S. paludicola var. 

 Kaalaasi K. Mull. (1915). Miiller regards 8. remota as a variety of 

 8. irrigua and reduces the var. alpina to synonymy under it; and he 

 includes under the var. Kaalaasi some of the Swedish plants which 

 Arnell and Jensen referred to 8. hyperborea. In a recent letter from 

 Dr. Arnell he writes that he now regards the var. alpina as an aggre- 

 gate, made up in part of S. hyperborea and in part of 8. paludicola; 8. 

 remota he considers an unimportant form of 8. irrigua and the var. 

 Kaalaasi as a scarcely more important form of 8. paludicola. These 

 divergent views clearly indicate that the plants in question are in 



