THE PHYTOLOGIST. 



No. XLIL 



NOVEMBER, MDCCCXLIV. 



PmcE Is. 



Art. CCXLV. — On the British Species of Sphagnum. 

 By W. Wilson, Esq, 



The investigation of this difficult genus is more properly a task for 

 one who has uninterrupted leisure : but since the subject has recently 

 come under my special notice, I am induced to present the result of 

 my enquiries to your readers, reserving the details for the ^Manual of 

 British Bryology,' wliich it is ray intention ere long to publish. 



Mr. Valentine has long ago pointed out, in the ' Muscologia Not- 

 tinghamiensis,' a good diagnostic for S. cymbifolium. Dill. (S. obtusi- 

 folium, Hook. Sf Tayl.), residing in the cellules which constitute the 

 cortical layer of the ramulus. If these are carefully examined with 

 a good lens, they will be found to have a very curious lining of spiral 

 fibres coating the whole interior surface, except where the circular 

 pores are found. This lining, and the circular pores, are analogous 

 to those of the cellules which compose the leaves. 



S. compactum (Biidel), found in Oxton-bog by Mr. Valentine, has 

 the cellules of the ramulus quite destitute of spiral lining. The leaves 

 are different in shape from those of S. cymbifolium, ovaie-ohlong, the 

 upper portion almost subulate, and the apex always prcem or so-den- 

 tate. The leaves of S. cymbifolium vary in shape from roundish to 

 elliptical, generally boat-shaped, sometimes recurved in the upper 

 half, when they greatly resemble those of S. squarrosum, but may al- 

 way be known by their very concave and entire apices, and by the 

 prominent cells at the back of the leaf, just below the apex. S. com- 

 pactum and S. cymbifolium are the only species known to me which 

 have the margin of the leaf minutely denticulate (especially towards 

 the apex) : all the other species have the margin entire and cartilagi- 

 nous, most evidently so in S. cuspidatum, Ehrh. 



S. squarrosum (Pers.), has the leaves recurved and very acute at 

 the apex : it can only be confounded with the squarrose variety of S. 

 cymbifolium. 



S. contortum (Schultz) is a difficult species, as I judge from the 

 circumstance of its having been described in the * Bryologia Gerraa- 

 nica,' " foliis ovato-acuminatis falcato-stihsecundis nitidis, ramulis 

 recurvato-contortis." The name itself seems to be unhappy ; since it 



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