PLEUROCOCCUS VIRIDIS. 17 



tain other distinctions, the Algae are further subdivided. 

 One of these subdivisions of the Algae is the Chlorophyceae, 

 to which Pleurococcus belongs. 



To complete the following study it will be necessary to 

 have pieces of wood bearing Pleurococcus; iodin; and 

 alcohol. 



LABORATORY WORK. 

 GROSS STRUCTURE. 



Taking a fresh specimen, observe : 



1. The color. 



2. The evenness with which the plant overspreads the sup- 

 porting surface. 



3. By using the scalpel observe that the plants are easily 

 removed from the surface on which they grow. 



4. The pulverulent appearance, as if dusted or sanded upon 

 the surface. 



5. The appreciable thickness reached in some spots, causing 

 it to separate in scales in a dried specimen. 



Place a piece of bark with the Pleurococcus in a small 

 quantity of alcohol; after an hour or more notice: 



6. The color imparted to the alcohol by the coloring-matter 

 of the plant, the chlorophyll. 1 



7. Observe the plants after the chlorophyll has been removed. 



MINUTE STRUCTURE. 

 I. NUTRITIVE OR VEGETATIVE STRUCTURES. 

 Mount, and under low power observe: 



1. The dust-like particles into which it separates. 



2. The various sizes of the particles. 



1 Some less common forms of unicellular Algae, as well as many more 

 complex ones, are red or purple from additional coloring-matter. 



