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generally split up the side, when it is called dimidiate; or, 

 when perfect the whole way down, it is called mitriforin. These 

 distinctions often afford good generic characters. 



(After speaking at some length on the character of cells, and 

 giving the various theories that had been started to accoiint 

 for their origin and multiplication, as well as the various 

 appearances they presented, Mr. Sansom proceeded to remark,) 



The bladders of all cellular tissue are, I believe, considered 

 as entirely closed up ; and it is generally supposed that the 

 various kinds of markings result from either depressions or 

 swellings on the surface. Mr. Valentine, however, describes 

 the cells of Sphagnum acutifolium as containing an aperture 

 tolerably distinct, which is situated at the upper end of the 

 cell, and stands off obliquely, appearing like a minute trun- 

 cated cone. He states, that an easy way to observe it is, to 

 press out the air contained in the cells, which escapes from 

 the aperture in a minute bubble. 



The simplest form, that of membranous cellular-tissue, was, 

 until lately, supposed to be the only one found in these plants. 

 But anatomists are now able to trace many modifications of 

 the normal form of cell. One of the most highly organized 

 Mosses is the Sphagnum of our bogs, which affords many 

 interesting examples of cellular tissue. In the year 1779, 

 Molhenhauer stated that the cells, of which the leaves were 

 composed, were marked by fibres twisted spirally, — now named 

 " fibro-cellular tissue." This theory was denied, the markings 

 being supposed to be the remains of decayed cells broken up ; 

 and it was considered as exploded, until about the year 1827, 

 when Messrs. Lindley and Griffiths confirmed Moldenhauer's 

 news. 



Schleiden regards the spiral condition of cells as universal. 

 The cells of the leaves are very thick-sided, and pierced by 

 wide or funnel-shaped pore canals in Blcranum Schraderi 

 Sjmrium, fyc. These spiral and porous formations are still 

 More conspicuously displayed, not only in Sphagnum but in 



