the Strumella disease, is the presence in the latter of small black 

 nodules, scattered over the surface of the yellowish area which 

 marks the extent of the lesion. In young infections of the type 

 described the dark nodules are either aborted or rudimentary 

 fruiting pustules No fertile pustules have ever been found in - 

 these young infections, but spore production occurs in the later 

 * stages of the disease. The yellowish-brown color is caused by 

 the whitish, or very pale buff-colored vegetative body, or my- 

 celium, of the causal fungus, which is covered only by the thin 

 external layer of cork cells. If some of this cork layer is re- 

 moved from the advancing edge of the lesion, the mycelium 

 exposed will show its pure white color, but in more central and 

 older parts the mycelium has changed to a pale buff color. In 

 general it is lighter in color than the mycelium of the chestnut 

 ■blight fungus, and definite ''fans" characteristic of the latter are 

 not noticeable. Lesions of this type have been found on shoots 

 up to 4 or 5 inches in diameter, and varying from minute inci- 

 pient infections to those completely encircling the trunk. The 

 young infections are much more obscure on older or rough- 

 barked trunks, but there is generally sufficient difference in color 

 to indicate the extent of infection. 



Two forms of the disease may be recognized with further 

 development of the trouble : first, the canker type, in which the 

 progress of the fungus is slow with a more or less pronounced 

 formation of callus at the advancing edge of the lesion ; second, 

 the diffuse type, in which the fungus spreads more rapidly, kill- 

 ing the tissues so quickly that the formation of callus is not 

 possible. Apparently it was only the conspicuous canker type 

 that was observed and described by Buckhout. 



In the well-defined canker there may be more or less zonal 

 growth (fig. 7), as the result of the repeated formation of cal- 

 lous tissue at the advancing edge, but it is the exception for the 

 callus to check the advance of the fungus. The lesion is gen- 

 erally extended more rapidly lengthwise of the trunk than trans- 

 versely, thus giving rise to cankers of somewhat elliptical out- 

 line (figs. 2 and 3). Cankers five feet or more in length have 

 been observed on trunks of chestnut trees 6-8 inches in diameter 



