OAK BARK- BLISTER. 481 



5. Aglaospora taleola, Tul. 

 (Oak Bark-blister.) 



The bark of oaks that still possess a smooth cortex, 

 becomes brown in patches, either on one side only, or all 

 round, and the affected part dies. The dead bark may be 

 either in little patches surrounded by living bark, or may 

 extend to a yard and more along the -stem. The diseased 

 places vary in breadth, being pointed at their upper and lower 

 extremities. The mycelium grows in the cortex, and pene- 

 trates also into the sapwood, which may become brown and 

 die ; the heartwood is not affected. 



Between the diseased and healthy tissues, a broad zone of 

 cork develops, which excludes water from the inner tissues. 

 The border of the diseased cortex therefore dries up and 

 produces no sporocarps. Between this dry border zone and 

 the rapidly decaying bark, cracks occur. The cortex under 

 the cork, which persists for a few years, decays and is finally 

 thrown off. The cankered spot thus produced quickly forms 

 a callus and heals up. 



In the second year of the disease, round or oval sporocarps 

 appear in the cortical parenchyma, under the cork. In the 

 midst of them, one or two (rarely three) little prominences 

 pierce the cork zone and exhibit openings of one or several 

 perithecia surrounded by white powdery conidia. The sporo- 

 carps in the cortex consist of dark brown pseudo-parenchy- 

 matous mycelia. The bottle-shaped perithecia, containing 

 ascospores, protrude from this mycelium. As a rule, several 

 of these ascospores coalesce. 



It is not yet decided whether or not this infection does any 

 injury to the affected parts. 



Pestalozzia Hartigii, Tubf. (p. 460), attacks young broad- 

 leaved plants in nurseries and on natural regeneration areas. 

 It is commonest on 2 5 years old beech, maple and ash, 

 which it eventually kills. The disease runs the same course 

 as that already described for conifers. It was very prevalent 

 in different parts of Germany during the wet summers of 

 1888, 1892, 



F.P, I 1 



