CHAPTER II* 

 MOLDS 



Fungi in General 



A sharp line cannot be drawn between the bacteria and the fungi. 

 Certain border groups such as Leptothrix and Actinomyces, filamentous 

 forms in which branching and even the production of differentiated 

 spores occur, are sometimes described as bacteria and sometimes as 

 fungi. From the microscopic point of view, forms in which the cells 

 can be handled as bacteria by cover-glass staining may be conveniently 

 treated by bacteriologists. Forms in which the cells are larger, with 

 definite walls, vacuoles, and cell sap, in which the cells collapse when 

 dried and lose their distinguishing characters, may be better treated 

 as fungi. No rule holds for all groups. 



With some exceptions, there is, among the cells of the true fungi, 

 a differentiation' of function into vegetative or assimilative ceUs and re- 

 productive cells. The fungous body is usually composed of threads 

 (technically called kyphcB, singular, hypha). These hypha usually 

 branch in more or less complex manner forming networks or webs, 

 collectively called mycelium. Hyphas may be one-celled or composed of 

 many cells placed end to end as shown by the cross walls, called septa, 

 seen in them. These threads grow either by the formation of new cells 

 at the growing tips (called apical growth) or by the division of cells in 

 the hypha {intercalary growth). The fungous cells rarely divide in 

 three planes to produce solid masses of cells. Both vegetative and 

 reproductive masses are formed in great variety from such hyphse. 

 Often the thread-like character is almost or quite obliterated in the ripe 

 masses, which may be fleshy, woody, carbonaceous, leathery and 

 even horn-hke in texture, as seen especially in the mushrooms, bracket- 

 fungi, etc., but even in such cases the early stages show the structures 

 to originate from masses of fungous threads. 



• Prepared by Charles Thom. A. Guilliermond has furnished the section on " Cytology of 

 Molds." 



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