HOW TO KNOW THE FRESH-WATER ALGAE 



DIVISION or PHYLUM Several orders may be grouped to form 

 a major category known as a Division or Phylum of the plant kingdom 

 (or of the animal kingdom as the case may be). Thus several orders 

 of the green algae constitute the division (phylum) Chlorophyta. In 

 many instances it may be convenient to subdivide the phylum into 

 groups of orders called classes. Hence in the Chlorophyta there are 

 recognized 2 classes, Chlorophyceae and Charophyceae. In the key 

 which follows only the genus names are given, with illustrations of 

 1 or 2 common species. For this reason particular species in which 

 the student may be interested in identifying will not necessarily look 

 exactly like the ones illustrated. In so far as possible, the most dis- 

 tinctive features of the genus are shown in the illustrations. 



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