TYPES OF CRYPTOGAMS; THAiLOPHYTES 239 



266. Microscopic Examination Examine some of the cultures. 



Place a particle of the growth on a sUde, dilute it with a drop of 

 clear water, and place a cover-glass over it. Examine with the 

 highest obtainable power of the microscope, at least ^ iu. objective. 

 Note the forms and movements, also the sizes if practicable, of any 

 bacteria that are found. 



THE STUDY OF OSCILLATORIA i 



267. Occurrence. — Oscillatoria may occur floating in stagnant 

 water or on damp soil in ditches, roadsides, dooryards, paths, or 

 pots in greenhouses. Other nearly related plants occur on surfaces 

 of ponds sometimes covering considerable areas or adhering in small 

 spheres to submerged vegetation. Algae of this class are particu- 

 larly noxious in water supplies, as they partake of the nature of 

 bacteria, to which they are related. 



268. Examination with the Microscope. — After washing a particle 

 of Oscillatoria material in a drop of water to remove as much of the 

 earth as possible, place it in a clean drop of water, pull to shreds 

 with needles, cover, and examine under a power of 200 or more 

 diameters. 



Note the color and compare it with chlorophyll green. 



The filament is not one plant, but each of the cells which com- 

 pose it is one plant. They are packed together in the filament like 

 coins and sometimes may be found separating singly. The usual 

 mode of reproduction is by the separation of a number of adhering 

 cells as a short filament from one end of a longer one, and this 

 increases in length by the dividing of its individual cells. 



269. Movement. — At ordinary temperatures, favorable to growth, 

 movement may be observed in the filaments. Describe the move- 

 ment. What has it to do with the name of the plant ? 



1 A genus of the class Sdiizophycese. 



