212 



ALG.F. 



some other genera is very soft and gelatinous : the whole is usually 

 enclosed in a gelatinous envelope. The thallus is of filamentous struc- 

 ture, and either simple or ])ranched, the 

 secondary axes often arranged in whorls. 

 The main axis usually consists of a central 

 row of cylindrical cells surrounded by a 

 pseudo-cortex composed of smaller cells, 

 either placed in rows at right angles to 

 the axis, or parallel to it. It may, how^- 

 ever, consist of a single uncorticated row 

 of cells. Batrachospermum is a genus of 

 small green fresh-water Algae of great beauty 

 from the symmetry of their branching. The 

 stem grows by means of a cup-shaped 





^ ^ ^ % 



^^\ J D 



ci^v.^;^*" 



"II^.*?;'^, 





eg 



F?^ 



;>. 





BiS> 



^^ 



Fig. iZ<j.—Batrachos/"'7-jin(7n moniliforme Roth, a, portion of plant (x 30): b, portion with 

 cystocarps, c cecity. 150). (From nature and after Cooke.) 



