CHAPTER IV 



ALG^E 



ABOVE the Schizophytes and Mycetozoa is a large 

 assemblage of plants, sometimes all united under the 

 name of Thallophyta, but probably better divided into 

 two divisions of equal value, to which the rank of sub- 

 kingdom may with propriety be applied. The primary 

 division is based upon the presence or absence of 

 chlorophyll, and although a few of them which have 

 no chlorophyll are structurally similar to certain green 

 forms, and possibly to be considered as derived from 

 them, most of the forms without chlorophyll differ pro- 

 foundly in their structure from all green plants, and 

 may properly be relegated to a sub-kingdom of their 

 own. To the forms which possess chlorophyll, the 

 name of Algae has been given, while those where 

 chlorophyll is absent are known as Fungi. The two 

 low groups of green plants, the Protococcacese and 

 Volvocinese, which were considered in the last chap- 

 ter, are usually included with the Algae, and very prop- 

 erly so, as they doubtless represent the lowest members 

 of the sub-kingdom. 



The Algse are readily divisible into three main divi- 

 sions or classes, which are easily distinguished by their 

 color. All of them possess chlorophyll, but in two 

 of the classes there are other pigments present, giving 



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