XI. FUNGI 

 THEIR CLASSIFICATION 



384. What is a Fungus? — The fungi are all (with a 

 few doubtful exceptions) parasites or saprophytes which 

 have lost their chlorophyll and become incapable of sup- 

 porting an independent existence. Biologists are divided 

 as to their position in the genealogical tree of life. The 

 weight of authority at present seems to incline to the view 

 that they are degenerate forms derived from the algae, 

 while others regard them not as degraded descendants of 

 higher forms, but as representatives of the lowest primor- 

 dial types from which higher organizations have arisen. 

 If they represent a degraded and degenerate type, they 

 have been so modified by their parasitic habits as greatly 

 to obscure their relationship and render their position in 

 the general scheme of life a very doubtful one. They 

 represent an offshoot, or side branch as it were, of the 

 great evolutionary line, and so will be considered in a 

 chapter by themselves. 



385. Economic Importance. — On account of their im- 

 mense numbers, reaching at present the enormous total of 

 forty-five thousand known species, and of the parasitic habit, 

 which causes them to enter the bodies of other plants and 

 of animals, fungi are of great economic importance, espe- 

 cially the various microscopic forms grouped under the 

 head of Bacteria. By their rapid multiplication within 

 the blood and the tissues of their victims they produce the 

 most fatal and destructive diseases. They are the smallest 

 living organisms, and are always floating in the atmos- 

 phere, so that with every breath we draw, large numbers 



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