PART II. 



GENERAL BIOLOGY OF MICRO- 

 ORGANISMS. 



CHAPTER VII. 

 MORPHOLOGY AND CLASSIFICATION. 



The minute living things included under the general term 

 microbe, are exceedingly various in form and structure as well as 

 in respect to food requirements and physiological activity. 

 The number of different microbes is so great and so great are 

 the difficulties involved in the accurate observation of their 

 various features, that the biological relationships of many of 

 the various forms to each other are not yet determined, and 

 much of the generic and specific terminology in common use 

 rests upon insecure foundation. Nevertheless a certain kind 

 of order has developed in our conceptions of the grouping of 

 micro-organisms. 



Molds. The molds or hyphomycetes are multicellular or- 

 ganisms characterized by the formation of a network (mycelium) 

 made up of branching threads (hypha), and by their special 

 fruiting organs. These threads vary from 2 to 7;* in width. 

 Within the group of molds the structure of fruiting organs is used 

 as the most important character from which to determine relation- 

 ships. The phycomycetes, or algo-fungi, are characterized 

 by the presence of sexual reproduction in which the union of 

 two cells gives rise to resting cells, zygospores and oospores, 

 which are enclosed in a thick wall. The ascomycetes are char- 



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