8 



OUTLINES OF PLANT LIFE. 



2. Crush a bit of a Nostoc colony or a whole one of Rivularia between 

 two glass slips, remove the upper slip, cover with water and observe the 

 coiled (Nostoc) or radiating straight filaments (Rivularia) embedded in 

 the jelly. (Fig. 6.) 



12. Filaments of loose organization. — Of very near kin 

 to these plants are the oscillarias, which have received this 

 name from the pendulum-like swinging 

 of their tips (fig. 7). In them the cell- 

 walls remain connected more extensively 

 and more firmly, so that each cell is 

 disk-shaped, and the filament is much 

 less easily separated into its parts. 

 Moreover less of the wall has become 

 jelly-like, so that often this part is not 

 apparent and is difficult to see even when 

 the plants are looked at -with the micro- 

 scope. Even though invisible, it may 



Fig. j.—Oscillaria n, the ^ . ° ■' 



tip ; *, a portion of the be detected by the slippery feel of the 



middle of a nlament. Mag- 

 nified 540 diam. — After plants when rubbed gently between the 



Strasburger. '^ o j 



fingers. 



EXERCISE II. 



Oscillaria. i. Observe the color of a bit of Oscillaria. {\ 9.) 



2. With needles tease out the specimen in a drop of water on a glass 

 slip; observe the delicate thread-like form. (Fig. 7.) 



3. Transfer a bit of living Oscillaria to a small glass dish or white in- 

 dividual butter plate with a little water; protect it from drying up with 

 a cover; 24 hours later observe the position of the filaments. (^ 12.) 



4. Demonstration. Dip a considerable mass of Oscillaria in hot water 

 for a moment and put in a white butter plate with as small a quantity of 

 water as will cover it. As the water evaporates observe the color depos- 

 ited on the dish at the edge of the water. (If g. ) 



13. Feeding habits. — ^The feeding habits of the oscillarias 

 are worth notice. These plants are found in permanent pud- 

 dles and ditches where organic matter is decaying. The sig- 



