XIV.] ' ^ STONEWORTS. 43 



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In all the young cells of Cha?'a a nucleus of relatively 

 large size is to be seen imbedded in the centre of the pro- 

 toplasm, which is motionless, and is enclosed in a structure- 

 less cell-wall, composed of cellulose. As the cell grows 

 larger, the centre of the protoplasm becomes occupied by a 

 watery fluid, and its thick periphery, which remains applied 

 against the cell- wall, constitutes a sac, ox primordial tUricle, 

 in which the nucleus is embedded. In the larger cells the 

 primordial utricle is readily detached and made to shrivel 

 up into the middle of the cell by treatment with strong 

 alcohol. In the older cells the nucleus breaks up into a 

 number of portions. 



Numerous small green bodies — chlorophyll grains — are 

 embedded in the outer, or superficial, part of the primordial 

 utricle, and they increase in number by division, as the 

 cell enlarges. These chlorophyll grains are composed of 

 protoplasmic matter, which frequently contains starch gra- 

 nules, and is impregnated with the green colouring sub- 

 stance. 



During life, the layer of the primordial utricle which 

 lies next to the watery contents of all the larger cells is in 

 a state of incessant rotatory motion, while the outermost 

 layer which contains the chlorophyll grains is quite still. 

 In the large cells, so long as the nucleus is discernible, it is 

 carried round with the rotating stream. 



The antheridium is a globular spheroidal body with a 

 thick wall, made up of eight pieces, which are united by 

 interlocking edges. Tlie four pieces which make up the 

 hemisphere to which the stalk of the antheridium is at- 

 tached, are foursided, the other four are triangular. From 

 the centre of the inner, concave face of each piece a sort of 

 short process, the handle or manubrium, projects into the 

 cavity of the hollow sphere. At the free end of the manu- 

 al. 28 



