EUROPE AND NORTH AMERICA. 1 9 



cymbifolium will soon convince any one that it is a character on 

 which no reliance can be placed. As the purpose of the fibres 

 seems to be to preserve the shape of the vesicular cells and support 

 their delicate walls, we should naturally expect to see them most 

 abundant in the compact or denser forms, and such we find to be 

 the case, for in the short, close-branched forms of S. acutifolium the 

 cells of the stem leaves are fibrillose throughout, but in the tall, 

 slender forms they are altogether absent. 



The pores or foramina stand near the adjacent cell walls, and are 

 usually found on the posterior surface, but in S. tenellum they are on 

 the anterior, and in a few species both front and back are perforated, 

 as in S. rigidum. Their size varies in different species ; thus in 

 •S". acutifolium and cymbifolium they are very large, in S. subsecundum 

 and cuspidatum very small. Besides these, Russow calls attention 

 to larger apertures which become visible after treatment with iodine 

 and sulphuric acid, and indicate more extensive resorption of the 

 cell membrane ; thus in the lower part of a branch leaf of 

 S. fimbriahim so treated, these large openings reach across the 

 whole width of the cell. The word lumen is applied by continental 

 authors to denote the clear space in the interior of a cell through 

 which light is transmitted, or the space bounded by the internal 

 lining of the cells. 



In vS". fimbriatum, slriclum, Lindbergii, and others which have 

 stem leaves fringed at the apex, this appearance is due to resorp- 

 tion of the membrane of the marginal hyaline cells, and con- 

 sequent projection of the intermediate parenchym cells. 



The bracts or leaves of the perichaetium which surround the 

 elongated receptacle of the fruit, are much larger than the other 

 leaves of the plant, and in areolation are intermediate between 

 those of the stem and branches, though coming nearest to the 

 former ; their chlorophyllose cells usually present deficiencies in the 

 thickening layers of their walls, and these standing opposite each 

 other resemble imperforate pits, not unlike the dotted pleurenchyma 

 of the wood of conifers, and a similar condition is observable in the 

 walls of young axile cells of the Sphagnum stem (Hofmeister's 

 < Higher Cryptogamia,' pi. xvii. fig. 9 b). 



The bracts of the male inflorescence correspond with the branch 

 leaves in structure, though they are usually broader and shorter ; 

 but they frequently are adorned in addition with rich colours, which 

 vary according to the species. 



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