— 6— 



ish, not infrequently associated with 5. palustre, from which it is not 

 easily distinguished without microscopical examination. 



Var. a/fine (R. & C. ) Warnstorf, 1889. This aspect of our species, 

 first proposed as an independent species (5. affine) and well charr 

 acterized by Renauld and Cardot^'\ was correctly interpreted by 

 Warnstorf. It differs from typical plants only in the complete lack 

 of fringe-fibrils on inner walls of its hyaline leaf cells, in which char- 

 acter, as already noted, all degrees of transition are found. Its re- 

 tention as a variety is desirable for practical reasons, as calling atten- 

 tion to this direction of variation and preventing confusion of this with 

 the following species, S. palustre. From that species our variety is 

 distinct by several characters, any one of which may in occasional 

 specimens be found somewhat less strongly marked than normal. 

 Most reliable is the leaf section which in 5. imbricatum, as already 

 noted, shows chlorophyll cells equilaterally triangular with hyaline 

 cells very strongly convex on the dorsal surface, while 5. palustre has 

 chlorophyll cells isosceles triangular with short base and hyaline cells 

 much less strongly convex on dorsal surface. The hyaline cells of 

 the branch leaves of 5. imbricatum show a membrane on the inner 

 surface relatively more porose than that of 5. palustre (at any rate in 

 the case of the varietv and the typical plants found within the va- 

 riety's range), having large pores in a single row in each cell, even in 

 those of the central part of the leaf, a condition foreign to 5. palustre. 

 This character of 5. imbricatum is admirably snown by Roth's figure^^^ 

 though he gives no corresponcing figure of S. palustre with which to 

 compare it. Similarly the outer membrane of the cortical cells of the 

 stem of S. imbricatum is relatively more porose : in this species I have 

 counted up to 10 pores per cell. The stem leaves of S. imbricatum 

 are very constant in smaller size than in 5. palustre, in a more spatu- 

 late or nearly quadrangular and les^ oval form, more distinct hyaline 

 margin and complete lack of fibril -bands in hyaline cells, points again 

 well illustrated by Roth's figures/'^^ In the perichaetial leaves the 

 border region of normal alternating cells is relatively narrower in 

 5. imbricatum. Relying primarily upon the leaf section, but taking 

 into consideration at the same time the other points mentioned one 

 should have no trouble in separating 5. imbricatum var. affine from the 

 next related 5. palustre. 



In spite of Warnstorf's correct identification of this variety, it is 

 questionable whether he fully understood it, as his 5. degenerans^^^ and 



(1) Rev. bryol. 12: 44. 1885. 



(2) Die europaeischen Torfmoose, pi. ly Jig. M. 1906. 



(3) L. c, 1ig. So,; cf. la. 



(4) Bot. Centralbl. 42: 102. 1890. 



