NOSTOC. 



THALLOPHYTES; ALG^EJ CYANOPHYCE^. 



PRELIMINARY. 



Nostoc may usually be recognized by means of the 

 dirty bluish- or blackish-green jelly-like masses occurring 

 on damp earth, or on water plants, or in free roundish 

 lumps, either floating or submerged in stagnant water. 

 During periods of greater dryness the jelly-like masses 

 frequently form rather dry and flake-like coatings on the 

 earth at the bottom of pools that are becoming dry. Other 

 members of the Cyanophyceae, the group of Algae to which 

 Nostoc belongs, are often found in bluish-green jelly-like 

 balls and bear considerable resemblance to the Nostoc 

 masses. Such forms are Glceocapsa, Cylindrospermum, 

 Clatherocystis, Glceotrichia, and Rivularia. ^ 



LABORATORY WORK. 

 GROSS STRUCTURE. 



1. Examine one of the colonies, observing: 



a. Color, as seen in reflected and in transmitted light. 



b. The jelly which encloses the plants. 



2. Sketch one of the masses. 



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