228 THE FUNGI 



We shall consider five classes in the series of the fungi among 

 the thallophytes (see Outline of Classification, p. 155). 



Class V. The bacteria, or Schizomycetes. 

 Class VI. The yeasts, or Saccharomycetes. 

 Class VII. The alga-like fungi, or Phycomycetes. 

 Class VIII. The sac fungi, or Ascomycetes. 

 Class IX. The basidia fungi, or Basidioinycetes. 



CLASS V. THE BACTERIA, OR SCHIZOMYCETES 



251. The bacteria. The bacteria are the smallest living 

 beings known. The single cells of many species are less than 

 one ten thousandth of an inch in diameter, and some are very 

 much smaller still. Most of the bacteria are one-celled. Some 

 types are spherical or oval, some are straight or. slightly bent 

 rods, and some are spirally twisted forms of various lengths 

 (Fig. 206). Certain species are provided with numerous cilia and 

 are actively motile. The cells may be loosely joined together 

 in chains or collected in jelly-like masses or colonies, which are 

 sometimes brightly colored, yellow, red, blue, or green. Some of 

 the bacteria are filamentous and made up of rows of cells. The 

 cells are very simple in structure, since they do not have a 

 clearly defined nucleus, and in this important respect they 

 resemble the blue-green algce, from which they are believed to 

 have been derived (Sec. 211). 



The cells of the bacteria multiply by simply splitting apart, 

 which gives them their name of Schizomycetes, or fission fungi. 

 These cell divisions, under favorable conditions, take place in 

 some forms as frequently as once every half hour, and the de- 

 scendants from a single individual may number many millions 

 in a few days. The bacteria are only limited in their remarkable 

 powers of multiplication by lack of food or other unfavorable 

 conditions. Many bacteria have the power of developing thick- 

 walled resting cells, or spores, within the parent cell, which can 

 survive a temperature above the boiling point of water and also 



