PROTOPHTTA. 113 



filaments. Some are amber-colored, some brownish, some 

 bluish-green. The species of Oscillaria (Fig. 49, J5) are 

 mostly dark- green filaments collected into felt-like masses 

 floating on the surface of the water, or growing on wet 

 earth or the wet sides of watering-troughs, etc. A pecu- 

 liarity of these plants is their power of oscillating from 

 side to side, while at the same time they move forward. 

 In this manner they are enabled to travel considerable dis- 

 tances. 



232. In Rivularia the filaments are generally arranged 

 radially in little rounded masses. One of these (Rivularia 

 fiuitans) is often very abundant in lakes and slow streams, 

 the little floating greenish balls being a millimetre or less 

 in diameter. Other species occur as green slimy masses, as 

 large as pin-heads, on the stones and stems of water-plants 

 in ponds and brooks. 



233. Related to the foregoing, but probably not falling 

 within thisbranch, are the bright-green "Green Slimes" which 

 have been known under the name of Protococcus. They 

 are invariably one-celled plants, and the cells are much 

 larger than in any of the preceding. They occur com- 

 monly on damp walls and rocks and the sides of flower- 

 pots in greenhouses and conservatories, and in wet weather 

 on wooden walks and the roofs and sides of houses. 



234. One species of Prptococcus (P. nivalis) is the noted 

 Red-snow Plant which in the high north latitudes often 

 covers the snow, giving it a reddish color. It also occurs 

 on the mountain-tops in lower latitudes. Although really 

 a green plant, its color is reddish in one of its stages. 



235. In their inodes of multiplication these species of 



