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PART III. 

 BIOLOGY OF THE MICRO-ORGANISMS. 



Even at an early period, when elaborate experi- 

 mental investigations on the subject of the vital 

 peculiarities of the fungi were wanting, and when the 

 attempt was made mainly by philosophical speculations 

 to satisfy the already existing active interest in the signifi- 

 cance and mode of life of the fermentative organisms, a 

 definite and very important r6le in the economy of nature 

 was ascribed to the class of the fungi, and efforts were 

 made to bring the vital phenomena of the fungi, in so 

 far as they had been observed, into unison with this role. 

 These earlier views have latterly been confirmed in their 

 essential points by recent investigations and experiments ; 

 but in certain details marked differences have been 

 found. 



The view as to the teleological function and signi- Former view* 

 ficance of the fungi rests chiefly on the absence of biological re- 



chlorophyll; and this at once brings the fungi into 

 marked contrast with all other plants characterised by plants and 

 the presence of chlorophyll. While the latter, including 

 the algae, which are so closely allied to the fungi, obtain 

 the necessary carbon and nitrogen from the carbonic 

 acid, ammonia, and nitric acid which surround them, 

 and build up from these simple compounds with the aid 

 of the chlorophyll, the complex nitrogenous and carbona- 

 ceous materials which they contain ; and while these 

 plants are consequently able to assimilate their nutrient 

 materials from water, for example, which contains the 

 necessary mineral substances, and from the air, which 

 contains carbonic acid and ammonia; the fungi, on 

 account of their want of chlorophyll, cannot live in the 

 same manner, but require previously formed organic 

 substances in order to replace the waste products, and 



