636 



VITAL ACTIONS OF THE LOWER FUNGI. 



further they are completely surrounded by fluid media, 

 so that an extensive formation of mycelium or fructifica- 

 tion can never occur. On the other hand, the chemical 

 composition as well as the temperature of the juices of 

 plants furnish better conditions of existence for the 

 mould fungi, and here, as in the case of insects, they 

 find an opportunity of quickly penetrating through the 

 whole mass of the body attacked, and of thus bringing 

 the mycelial threads into contact with the free air. 



Parasitic 

 yeast fungi. 



B. The Budding Fungi as Infective Agents. 



Parasitic budding fungi have never as yet been 

 observed in plants, and in animals they occur extremely 

 rarely, and then only as epiphytic parasites. The only 

 known case of the latter kind is that of the fungus of 

 thrush, which for a time was looked on as a species of 

 mycoderma. Large numbers of yeast sells also at times 

 occur in the stomach and intestines of man, and pro- 

 bably on account of the plentiful supply of saccharine 

 nutriment, can keep up fermentation for some time, 

 and can thus occasion certain disturbances. 



Parasitic 

 bacteria. 



In plants. 



C. Fission Fungi as Causes of Disease. 



In contrast to the mould fungi, the bacteria almost 

 never attack higher plants, while warm-blooded animals 

 very frequently serve as their hosts. In the affection 

 known as the yellow disease of hyacinths in Holland, we 

 have however, according to Wakker,* an exception to this 

 rule in that an accumulation of yellow gelatinous bacterial 

 masses occasions the disease of these plants. The low 

 temperature and the chemical composition of the vegetable 

 juices is evidently very unfavourable for the development 

 of bacteria, more especially as the cell juices are almost 

 always distinctly acid, and thus protect the plants against 

 the bacteria, which are so sensitive in this respect. 

 Further, the cellulose which surrounds each individual 



* Botan. Centralbl., vol. xiv. 



