1910-1911.] Notes on Parasitic A seamy cetes. 333 



Yl,— NOTES ON PARASITIC ASCOMYCETES.—Vkkt I. 



By Mr D. A. BOYD, Corresponding Member. 



{Bead Jan. 25, 1911.) 



The group of fungi known as the Ascomycetes includes a very 

 large number of species, the vast majority of which are of 

 comparatively minute size, and either occur as saprophytes on 

 dead vegetable matter or grow on the ground. Numerous 

 other species, however, are true parasites throughout the 

 whole period of their existence, and sometimes appear in 

 such abundance as to occasion considerable injury to trees, 

 shrubs, or plants, in forest, field, or garden. Others are 

 merely " wound parasites," which can only obtain access to 

 the tissues of their host at some point where the bark has 

 already been bruised or broken ; while others exist as 

 parasites during the early period of their life, but become 

 saprophytic when they reach mature development. 



Although exhibiting much diversity in form and structure, 

 the numerous species of Ascomycetes agree in possessing one 

 constant characteristic — viz., their spores are always pro- 

 duced in the interior of enlarged cells known as " asci." 

 Each ascus or mother-cell may be described as resembling a 

 small bag, in which are usually contained a definite number 

 of spores, most commonly 8, but in some species 2, and in 

 others 4, 16, 32, or even a still greater number. 



Owing to the impossibility of dealing in the scope of a 

 single paper with so wide a subject as is suggested by the 

 title of this communication, it will be necessary for us in 

 the meantime to confine our attention to some of the more 

 common or notable species of Ascomycetes which are truly 

 parasitic at every stage in their life-history. These are 

 included in 5 families — viz., the Exoascacese, Perisporiacese, 

 Pyrenomycetes, Hysteriaceae, and Discomycetes. For the 

 present we must refer to the first two alone, leaving the 

 other three to be dealt with in a subsequent paper. 



In the Exoascacese the asci are developed from an accumu- 

 lation of mycelium formed immediately beneath the cuticle of 



