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A TEXT-BOOK OF BOTANY 



(3) Sexual reproduction is indicated by 



>-Mi:>Hl>-^ 

 indicating that two special cells (gametes) are produced by 

 the plant, that these two fuse to form one (oospore) , which 

 then produces a new plant. 



66. Cladophora. This plant is found attached to 

 sticks and stones at the edge of ponds or lakes, and is often 



so abundant as to form thick 

 mats of long anchored filaments. 

 It is easily distinguished from 

 Ulothrix, for it is a much coarser 

 plant and branches freely (Fig. 

 98). It is mentioned here both 

 because it is common and be- 

 cause it illustrates a branching 

 filamentous body. Just as in 

 Ulothrix, reproduction in Clado- 

 phora is carried on by means of 

 swimming spores, and also by 

 the fusion of swimming gametes 

 to form oospores. 



67. CEdogonium. The fila- 

 ments of CEdogonium are long 

 and simple, the lowest cell act- 

 ing as a holdfast, as in Ulothrix 

 and Cladophora. In each cell a nucleus may be seen (Fig. 

 99), and apparently several chloroplasts; but really there 

 is only one large complex chloroplast. 



Any one of these cells may produce within itself a single 

 large swimming spore, which escapes from the mother-cell 

 into the water (Fig. 99, C). At its more pointed clear end 

 there is a little crown of cilia, by means of which it swims 

 about rapidly. These spores finally anchor themselves, 

 and each one produces a new filament (Fig. 99, D and #). 



FIG. 98. Cladophora: a branch- 

 ing filament, each of whose 

 cells contains several nuclei. 



