CHAPTER 15 

 SPORE DISCHARGE AND DISSEMINATION 



While the production of mature viable spores may be considered the 

 climax in the life of a fungus, the wide dissemination of these spores is 

 often a requisite to the perpetuation of the species. Frequently, this is 

 assured by the production of enormous numbers of spores, which increases 

 their chances of falling into favorable environment. The chief agent of 

 dissemination among the fungi is air currents. Water, insects, and other 

 animals play lesser roles in the natural dispersal of spores. Light, dry 

 spores are usually disseminated by air currents, which may be strong 

 enough to loosen them from the fruiting structures on which they are 

 produced. On the other hand, spores borne in a gelatinous matrix are 

 better adapted to transmission by rain, by insects, or by other animals 

 which come in contact with them. Of particular interest are those fungi 

 which possess certain special mechanisms for discharging their spores 

 away from the fruiting structures. A study of the functions of these 

 special adaptations must of necessity be based upon a knowledge of the 

 structure of the fruit bodies which produce the spores. 



METHODS OF SPORE DISCHARGE 



The discharge or liberation of spores from the reproductive structures 

 which produce them may take place by (1) violent expulsion of the spores 

 or sporangia, due to internal pressure, (2) motility, as in the zoospores of 

 the aquatic Phycomycetes, and (3) external forces of the environment. 



The violent discharge of spores, sporangia, or other reproductive bodies 

 depends upon the development of considerable pressure within the fungus. 

 The structure of the fungus cell is very similar to that of algae or the 

 parenchyma of the higher plants. The vacuole is filled with water and 

 its dissolved compounds, such as sugars, salts, and amino acids. Foods 

 in the cell m^ay be in the form of sugar, glycogen, or oil. If the amount of 

 soluble materials, such as sugar, is increased, the cell has a tendency to 

 absorb water. As a result, the cell becomes more distended and may 

 continue to swell until the elasticity of the cell wall is exceeded. The 

 increase in sugar concentration may be the result of the hydrolysis of 

 glycogen. 



Discharge of sporangia. The genus Piloholus illustrates a remarkable 

 combination of adaptations for the production, discharge, and subsequent 



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