FRESH-WATER ALG^. 99 



branched, and in both cases it consists of rows of cells which 

 multiply by intercalary growth, while the terminal cells elongate 

 into hyaline bristles. The slender filaments of ^dogo?iiiim 

 resemble those of Co?iferva at first sight, but are distinguished by 

 transverse parallel striae at one or other extremity of the cells 

 indicating the mode of increase. In Bulbochcete the growth 

 proceeds by continuous division of the basal cell, and the cell 

 membrane is usually punctate. 



In both genera the asexual reproduction is of the usual 

 character, but the sexual reproduction is varied. In yEdogoniiim 

 the plants may be monoecious, or dioecious, and the dioecious 

 species may be further divided, according as the male filaments 

 are derived from certain privileged cells in the female plant, or 

 are from the first distinct from the female filaments. The 

 Bulbochxte are divided into two sections, according to the shape 

 of the oogonia, whether globose or ellipsoid. The first section is 

 dioecious, and is further sub-divided according as the dwarf male 

 plants are unicellular or bicellular. The second section is sub- 

 divided into monoecious and dioecious species. 



The Confervece^ like the j^dogniece^ consist of rows of cells or 

 segmented filaments, which either remain unbranched as in 

 Chcetomo7'pha^ or become branched as in Cladophora^ Stigeodoiihmi^ 

 Draparnaldia, and ChcBtophora. With reference to their repro- 

 duction, it is only known that macro- and micro-zoogonidia are 

 formed in the cells of the filaments ( ChcBtomorpha^ Cladopho7'a)j 

 the sexual significance of which is still unknown ; and that in the 

 other above mentioned plants, resting spores are formed in 

 certain cells of the filaments. Pringseim suggests that they are 

 probably equivalent to oospores, but that they are produced 

 parthenogenetically. The UlvacecE are probably allied to the 

 ConfervecB. In them the cells are arranged so as to form a delicate 

 membrane ; whilst in the other genera the cells form slender fila- 

 ments of a soft membraneous nature. In C/uefo/norpha the long 

 filaments are interwoven either in lax tufts, or in dense strata, 

 each filament being curled, twisted, or bent somewhat irregularly. 



In Cladophora the filaments are irregularly branched and 

 curled, of a light membranaceous substance, and often forming 

 detached floating tufts. Some species are found in great abun- 



