GEEEN ALG^E. 



35 



focusing it is easy to show that the protoplasm is confined to a thin layer 

 lining the wall, the central cavity of the tube being filled with cell sap. In 

 the protoplasm are numerous elongated chloroplasts (cL), and a larger or 

 smaller number of small, shining, globular bodies (ol.). These latter are 

 drops of oil, and, when the filaments are injured, sometimes run together, 

 and form drops of large size. No nucleus can be seen in the living plant, 

 but by treatment with chromic acid and staining, numerous very small 

 nuclei may be demonstrated. 



When the filaments are growing upon the ground, or at the bottom of 



FIG. 21. A, C, successive stages in the development of the sexual organs of a 

 green felt (Vaucheria). ori.antheridium. or/, oogonium. D, a ripe oogonium. 

 E, the same after it has opened, o, the egg cell. F, a ripe spore. G, a 

 species in which the sexual organs are borne separately on the main filament. 

 A, F, x 150. G, x 50. cl. chloroplasts. ol. oil. 



shallow water, the lower end is colorless, and forms a more or less branch- 

 ing root-like structure, fastening it to the earth. These rootlets, like the 

 rest of the filament, are undivided by walls. 



One of the commonest and at the same time most characteristic species 

 is Vaucheria racemosa (Fig. 21, A, F). The plant multiplies non-sexually 

 by branches pinched off by a constriction at the point where they join 

 the main filament, or by the filament itself becoming constricted and sep- 

 arating into several parts, each one constituting a new individual. 



