Ch. X] THE GREEN ALG.E 415 



The Myxomycetes exhibit relations to animals so close 

 that some biologists have placed them in that group, and 

 this position is expressed in one of their names (Mycetozoa : 

 " the Fungus-animals "). The free locomotion of their amce- 

 boid plasmodia, and the ingestion of solid food, are animal 

 characteristics, but their elaborate sporangia and cellulose- 

 walled spores are wholly plant-like. 



Ecologically the Myxomycetes are free-moving sapro- 

 phytes. Phylogenetically, they show closest affinities with 

 the Flagellates, of which they perhaps represent a highly 

 specialized and peculiar colonial development ; and thus we 

 tentatively rank them (Fig. 275). It is not impossible, 

 however, that the colonial habit is primitive, the subdi- 

 vision into unicellular members being subsequent. 



Class 5. Chlorophyce.^ : the Green Alg.^ 



These comprise the Algae of bright or grass green color, 

 both microscopic and large. They live mostly in fresh 

 water, or in damp shaded places on the land, though a few 

 are marine. Some 9000 species are known, but none are 

 economically important. 



The Green Algse are most diverse in size, form, and habit, 

 as will appear under the different orders. Those of fresh 

 water, especially, present a variety and beauty which, in con- 

 junction with their ease of collection, has made them al- 

 ways very favorite subjects of study by those who are 

 moved by the genuine spirit of the naturalist. All in com- 

 mon possess well-differentiated cells containing bright green 

 chloroplasts wherein they synthesize their food. Their 

 reproduction is likewise diverse, but most of them possess 

 small free-swimming asexual zoospores which produce new 

 individuals directly. Usually, also, they possess sexual 

 gametes. These are sometimes alike (isogamous), and 

 smaller than the zoospores which they superficially resemble ; 

 and on conjugation they produce zygospores. In higher 

 forms the gametes are unlike (heterogamous) and ulti- 





