PHYLUM THALLOPHYTA 



9^3 



will realize that in no instance can a species be designated by more 

 than two words — viz., the generic and the specific. 



With regard to the value of bacterial species based upon biolog- 

 ical and not upon morphological differences, the remarks which 

 we wrote on this subject in regard to the Protozoa hold good here, 

 and need not be repeated, while we would refer the reader again to 

 the section on evolution in Chapter V., p. 112. 



The Regnum Vegetabile, or vegetal kingdom, is usually divided 

 into four great phyla or groups — -viz., the Thallophyta, the 

 Briophyta, the Pteridophyta, and the Phanerogamae, but of all these 

 only the first need concern us. 



The Thallophyta include a great variety of plants whose vege- 

 tative body may consist of one or many cells, forming a more or 

 less branched structure. 



These plants may be defined and classified as follows: — 



PHYLUM THALLOPHYTA. 



Definition. — ^Vegetabiles with a cellular structure, which is gener- 

 ally little differentiated, and reproducing asexually by division 

 and by spore formation or sexually, after conjugation, by oospores. 



Classification. — The Thallophyta may be divided into: — 



A. Thallophyta with chromatophores and often with chlorophyll — • 



Class I., Alg£B Roth, 1797. 



B. Thallophyta without chromatophores or chlorophyll — Class II., 



FungacecB Linngeus, 1737. 



There can be no doubt that the Fungacese are descendants of the 

 Algae, which, because of a saprophytic or parasitic environment, 

 have altered their food habits and have adapted themselves to new 

 methods of nutrition, and hence no longer require chromatophores 

 or chlorophyll, as they no longer manufacture their food with the 

 aid of sunlight, but subsist on decaying animal or vegetal material 

 rich in organic substances. 



They may be parasitic or saprophytic, or a form which is usually 

 parasitic may at times become a saprophyte, or vice versa. 



With regard to their origin, the three great divisions probably 

 differed in their evolution; thus the Schizomycetes are probably 

 derived from the Cyanophyceae, or Blue-Green Algae, while the 

 Phycomycetes and the Eumycetes stand in closer relationship with 

 the Chlorophyceae, or Green Algae; and it is because of this great 

 difference in origin that the Schizomycetes are kept apart from the 

 Fungaceae, and are classified with the Algae, although they are 

 often included in the loosely used term Fungi (auctores). 



Another less usual classification is to divide the Thallophyta into 

 two great groups, of which the first includes the Cyanophyceae and 

 the Schizomycetes, while the second embraces the Myxomycetes, 

 the Peridineae, the Conjugatae, the Diatomenae, the Heterocontae, 

 the Chlorophyceae, the Characeae, the Phycomycetes, the Phaeo- 

 phyceae, the Rhodophyceae, the Eumycetes. 



We will now turn to consider the Schizomycetes. 



