GREEN SLIME. 



Pleurococcus viridis. 



THALLOPHYTES; ALG^J CHLOROPHYCE^. 



PRELIMINARY. 



THE plant selected to illustrate the simplest phase of 

 plant life is found in all parts of the United States, and 

 even throughout the world. It grows upon the surface 

 of various objects, being often so abundant as to give 

 them a conspicuous green color, especially the north side 

 of old fences, barns, and the trunks of trees, becoming 

 more noticeable after a few days of damp weather. There 

 are several other closely related forms that may be used. 

 In fact almost any unicellular green plant will answer, 

 but this is the one most easily found. Pieces of bark or 

 wood bearing Pleurococcus plants may be kept dry for 

 use, and will give a fresh appearance when moistened 

 with water, and even retain vitality for a year or two. 



This plant belongs to the great group known as 

 Thallophytes, a group that is divided into Algae and 

 Fungi. The Algae are characterized by the presence of a 

 green coloring-matter known as chlorophyll. Upon the 

 basis of various combinations of colors made by chloro- 

 phyll and other coloring substances, as well as upon cer- 



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