222 MICRO-ORGANISMS AND FERMENTATION. 



through their development, acquires a dark brown or black 

 colour. Fungi belonging to this group play a part in bringing 

 about the decomposition of eggs. Zopf has identified a species 

 which recent investigations have shown to be capable of 

 sending germinal hyphse through the egg shell and membrane, 

 .and of gradually decomposing the albumen. O. Jensen has 

 observed that a species of Cladosporium promotes the rancidity 

 of butter on account of its power of splitting up fatty sub- 

 stances. Eriksson states that rye is sometimes attacked by 

 Cladosporium, and that the mould when consumed in rye 

 bread or in beer may prove pathogenic. 



Concerning these, or certain closely related forms, Zopf 

 detailed exact morphological investigations, accompanied by 

 numerous illustrations, in his memoir on Fumago, and also in 

 his work on the fungi. This black, soot-like fungus occurs 

 very frequently on plants. Frank correctly says : " We are 

 still quite in the dark with regard to specific differences, due 

 especially to the frequent polymorphism of these organisms, 

 and to the fact that the different evolution forms are scarcely 

 ever found together." 



Among the various fungi occurring on the vine, the two 

 following parasites have obtained an unenviable notoriety, on 

 .account of the great damage they cause : 



11. Oidium (Erysiphe) Tuckeri. 



This fungus, which is also called " the true mildew," forms 

 whitish spots, changing to brown, on the leaves and shoots of 

 the vine. These consist of mycelial filaments, from which 

 elliptical or oblong, colourless conidia separate, 8 /u long and 

 5 fji. thick. The mycelium spreads over the fruit, which is 

 gradually covered with a delicate growth of a grey colour, 

 while it thrusts through the fruit skin roundish suckers, killing 

 the epidermal cells. When grapes are attacked at an earlier 

 .stage, the epidermis is unable to keep up with the growth of 

 the contents ; it then gradually splits open like skin affected by 

 .scurf , the contents exude, and the grapes either dry up or putrefy. 

 'They may impart to wine a very unpleasant smell and taste. 



