Parasitic and Saprophytic Fungi in Orchards. 195 



the characters which makes the canker easy to recognize. This 

 together with the rings which the discs leave on the wood after 

 the stromata are broken loose, gives two characters which .nake 

 it possible for anyone to determine it. Even to the untrained 

 observer, these marks if once known, will lead to a proper diag- 

 nosis. CFig 4, a and b). 



In the Cook orchard, south of the Dairy building, this canker 

 occurred in abundance. Nearly all of the trees were cankered 

 to a greater or less extent. The large limbs were the ones usually 

 attacked. Sometimes the canker was well down on the trunk 

 of the tree on the lower side of the branches and extended far 

 out on the branches and twigs. In such cases large linbs were 

 entirely killed. 



Nummularia appeared in the exposure on May 2nd, and 

 again on May 9th. At the time when it began to appear small 

 masses of spores could be seen at the necks of the perithecia 

 on the stromata. It produces a loose cottony colony with a 

 brownish tinge, especially on the under surface. 

 3. Sphaeropsis malorum Pk. 



Sphaeropsis malorum is one of the most comnon fungi 

 that inhabits pome-fruit orchards east of the Rocky Mountains. 

 This is one of the forms whose pycnidia were found on twigs in 

 the orchards at Heath's near College View, and south of the 

 Dairy building. It is the cause of the "black rot" of the apple, 

 pear, and quince, and produces cankers on the twigs of these 

 trees. The small black pycnidia, just beneath the outer bark, 

 characterize this fungus, which occurs so abundantly in nearly 

 every orchard of this region. 



Diseased twigs are perhaps the m.ost abundant source of 

 infection. Infection may also be due to diseased fruits of the 

 previous year's crop. 



Scott* has shown that it is the principal cause of leaf-spot 

 of the apple, producing small brown patches. It is not commonly 

 the case that the pycnidia are formed on the leaves until after 

 they have fallen. 



At various times during the year diseased twigs were 

 brought into the laboratory and the fungus grown in planted 

 plates. The upper surface of the colony is a dirty gray and the 



•Scott. 1. c. 



