274 



COLLEGE BOTANY 



In reproduction it forms stationary bodies of definite form 

 which resemble fungi. These structures are characteristic of the 

 different species and are known as sporangia. They bear the 

 spores which under favorable conditions of warmth and moisture 

 give rise to ciliate, unicellular, animal-like cells which fuse and 

 form a new multinuclear plasmodium. 



Most of the species belonging to this division are sapro- 

 phytic, but some few are the causes of diseases of other plants. 

 The club root of the cabbage, a very important and destructive 

 disease, is due to one of these species. 



The Schizomycetes are the " fission fungi " or " bacteria." 

 They are extremely small, unicellular organisms, and are capable 



of multiplying very rapidly. They 

 are the smallest known forms of 

 lifa They are very similar in 

 structure and life history to the 

 Cyanophycece (page 261), but they 

 do not contain the coloring mate- 

 rials. Some of them are sapro- 

 phytes and others are parasites. 

 There is an enormous number of 

 species and we see the results of their activities on every hand. 

 They live on or in the food supply which they take in through 

 any part of the cell wall by means of absorption. However, the 

 food must first undergo a change as a result of the action of en- 

 zymes which are secreted by the organism. Some require air and 

 are known as aerobic forms, while others thrive best without air 

 and are known as anaerobic forms. Reproduction is by simple 

 fission andunder f avorablecircui.isitaiices is very rapid. Although 

 extremely small, they are among the most important forms of life. 

 They, together with fungi, cause the souring of milk, the ripen- 

 ing of butter and cheese, and the decay of fruits, vegetables and 

 meats. There are many species which cause diseases, of which 

 some of the most common are tuberculosis, anthrax, pneumonia, 

 diphtheria, typhoid fever and lockjaw. There are other species 



FIG. 124. (a) Types of mature Myxo- 

 mycetes; (b) and (c) stages in the devel- 

 opment of the plasmodium. 



