DEVELOPMENT OF PLANTS 147 



ized by sexual reproduction and that therefore there must be a 

 sexual fusion of the nuclei at some time in the life history of the 

 Plasmodium. The structure and life history of these plants is 

 so simple that it is possible that they may have been derived 

 from forms allied to the first forms of life upon the earth. The 

 common occurrence among simple animals and plants of motile 

 stages or zoospores in their life history certainly suggests that 

 possibly such forms may represent the first appearance of living 

 matter. 



Subdivision 2. Schizophyta or Bacteria and Blue Green Algae. 



As in the preceding group these forms are extremely simple 

 and possess some characters suggestive of the lower forms of 

 animal life. They have received the name of Schizophyta, mean- 

 ing splitting plants, owing to their common method of repro- 

 duction by division of the cell into two equal parts. There are 

 two important classes of Schizophyta: A, Bacteria; B, The Blue 

 Green Algae. 



Class A. Bacteria 



62. The Structure and Nature of Bacteria. — Bacteria are com- 

 monly known by such vague terms as microbes and germs. They 

 are, however, unicellular plants that are of almost universal dis- 

 tribution though more abundant about dwellings and less com- 

 mon in cold countries, at high altitudes and on the sea. They 

 include the smallest and simplest forms of plants, ranging from 

 scarcely 1/50,000 in. to 1/10,000 in. in diameter (Fig. 91). Such 

 forms would have many times more room in a drop of water 

 than a whale would find in New York harbor. So minute and 

 simple in structure are the bacteria that the real nature of the 

 plant body is somewhat a matter of dispute. The plants are 

 unicellular and surrounded by a delicate thin wall which in- 

 closes a colorless and slightly granular protoplasm (Fig. gi, A, 

 i). There is no nucleus comparable to that of the higher plants, 

 although indications of it are seen in a few scattered chromatin 

 grains. The cell content is very simple and totally lacking in 

 plastids and other differentiations with which you are familiar. 



