THE ALG.E 225 



288. Discussion. — (Edogonium is a plant of decidedly 

 higher type than Spirogyra. "While the nutrition of both 

 plants is much alike, (Edogonium shows a decided advance 

 over Spirogyra in the structure of the vegetative filaments, 

 inasmuch as these are not alike at both ends, but have a 

 definite cell which serves as a holdfast and a terminal cell 

 different from the others of the filament. 



The sexual reproduction of (Edogonium is accomplished 

 by the union of unlike gametes (sperm and egg-cell) and 

 is therefore higher in type than that of Spirogyra in which 

 the gametes appear to be alike. The small size of the 

 sperms enables them to accomplish the fertilization of 

 the egg with the expenditure of only a trifling amount 

 of material, and the motility of the sperms enables them to 

 reach the &gg quickly, instead of drifting against it as one 

 filament of Spirogyra drifts against another. Economy and 

 certaint}' in the process of sexual reproduction are features 

 of the progress of plants from lower to higher forms. 



In some species of (Edogonium the antheridia are pro- 

 duced on small short filaments called dwarf males. These 

 are developed from zoospores which attach themselves to 

 the female filament or to the oogonium. 



VAUCHERIA, ONE OF THE GREEN ALG.E 



289. Occurrence. — Vaucheria, or green felt, is one of 

 the rather widely distributed green algse, some species 

 being found in salt water and others in stagnant fresh 

 water, sometimes in fresh running water or on damp soil. 

 V. sessilis, the commonest species, occurs covering the 

 earth of pots in greenhouses. When growing on earth it 

 is rather easily recognized by its dark green color and the 



