EXOASCALES 



37 



condition which by some is supposed to ally them to the ascomy- 

 cetes of which they are commonly regarded a low degraded form ; 

 there is however little more reason for considering these as asci 

 than as sporangia. The spores thus produced possess greater 

 powers of resistance to desiccation ; they germinate to form bud- 

 ding yeast cells. The yeast plant is the active agent of all forms 

 of yeast, tho various species of bacteria are usually mixed with 

 them and share in the function of raising bread. The relation of 

 the various forms of yeast to the process of brewing has become 

 a subject of special study. Besides the family Saccharomycetaceae, 

 containing the yeast fungi, the order contains the family Endo- 

 mycetaceae with four genera which have heretofore been reported 

 only from Europe. 



LITERATURE.* 



Schroeter. Die natiirlichen Pflanzenfamilien i 1 : 150-156. 



Saccardo. Sylloge Fungorum, 8 : 916-922. 



Zopf. Die Pilze, 41 1-425. 1890. 



Bay. The spore-forming Species of the Genus Saccharomyces. 

 Amer. Nat. 27: 685-696. 1893. 



Golden. Fermentation in Bread. Bot. Gaz. 15: 204-209. 

 1890. 



Pasteur. Studies on Fermentation. (English translation.) 

 Macmillan & Co. 1879. 



Orders. EXOASCALES. 



The order Exoascales includes a number of parasitic fungi that 

 attack various plants, notably the drupaceous fruit trees. One of 

 the most common produces the " peach curl " frequently seen in 

 the young leaves of the peach. In this disease the leaves become 

 variously distorted and deformed and are covered with patches of 

 a reddish or sometimes a whitish color. In badly affected leaves 

 the leaf finally withers and shrivels up as if burned. Other species 

 are found on various plum and cherry trees producing deformities 



* The technical literature bearing on yeast as an economic factor in the 

 production of beer is enormous, and the continuous study of its conditions 

 and physiological activities constitutes the work of specialists in every 

 large brewery. 



