1911.] PUBLIC DOCUMENT — No. 31. 173 



ill color. On exaiiiiiiation in the fall these masses were found 

 to contain inycelium and spores similar to those found in other 

 gummy masses in the orchard. These chains of dark spores 

 produce many thick-wallod spores, or micro-sclerotia, as de- 

 scribed by Massee, and these thick-walled spores, or niicro- 

 sclerotia, in turn give rise to many small byline conidia, while 

 another form of the micro-sclerotia gives rise to a mycelium 

 which bears numerous conidia. In the gummy mass one finds 

 j)rcs{>iit many pycnidia of a brown color, similar in color to the 

 micro-sclerotia, and from their situation, color, etc., one would 

 take them for different stages of the same fungus. However, on 

 isolating these pycnidial bodies, which were tilled with myriads 

 of minute byline spores, and growing them on pure cultures, I 

 was unable to get any connection between the two; but I found 

 that the minute byline spores without exception gave rise to 

 other pycnidia and Alter naria spores; the AUernaria spores, 

 growing on the same mycelium as the pycnidia, in turn gave 

 rise to i\vcnidia and AUernaria spores. 



Histological Changes Accompanying Guniinosis, 

 The cut facing this i)age represents a cross-section of a dis- 

 eased twig of a i)each tree, showing two well-developed annular 

 rings and a third ])artly developed. This twig was probably at- 

 tacked by the brown rot fungus, together with Cladosporium and 

 a form of AUernaria. 



This section, which is a typical one, shows that the disease 

 did not destroy the cambium ring until the fall of the second 

 year, but the disease may have made its ai)pearance even a year 

 earlier. The noticeable feature in this illustration is that the 

 last layer of wood formed was very much thinner towards the 

 uninjured side of the twig than the injured side, and ibis ring 

 of wood is not complete near the area where guniinosis had 

 set in. There is also a noticeable thickening of the incomplete 

 I'ings of wood near the point of injury, a fact due probably to 

 the difference in tension occurring in the stem produced by the 

 injury from gummosis. The cambium, at the margin of the 

 diseased area where it has attempted to heal over, is also much 



