A MANUAL OF BOTANY 105 



Appearance. Examine by feeling and with the naked eye. 

 How do the fihxnients compare in size and color with those 

 of the algae already studied ? Observe whether it normally 

 floats free, or is attached. 



Structure. Examine (/^:>). Observe the color, also the 

 distribution of the chloroplasts, the thick cell walls, and 

 the oil globules. Trace a filament for some distance. Is it 

 simple or branched? Would you consider this plant more 

 or less complex than spirogyra? Give some reasons for the 

 answer. Where do the branches always originate with refer- 

 ence to the part of the cell from which they come ? What 

 shape has each branch ? 



Look carefully for cells in the filament that are divid- 

 ing. Where are they situated ? ( Cladophora grows in size 

 by the elongation of the cell tips with subsequent division. 

 Branches ai-e formed in the same manner. The plant rapidly 

 increases in size in this manner and by breaking up forms 

 new plants.) 



Associated algae. Commonly attached to the filament are 

 many small brown structures (diatoms) or one-celled brown 

 algae. Remember this when the diatoms are studied. 



Drawings. Make drawings showing the results of your 

 study. 



Reproduction. This alga reproduces by zoospore formation, 

 which always occurs at night and hence is seldom seen. 

 Single cells give rise to spores having cilia (called by the 

 above name) which move about for a time; then, after a 

 period of rest, germinate and form new filaments. Under 

 certain conditions these spores, also called zoogonidia, unite 

 (conjugate), producing an oospore (zygospore of many 

 authors), which in time produces a new filament. 



What advantage is the double method of reproduction? 



Nature of filament. The cells of this alga, while quite 

 similar to each other, do not all do the same work; certain 

 basal ones serving for attachment to rocks, etc., terminal 



