126 Staten Island Association of Arts and Sciences 



of the disease. Cultures were made from the affected trees, and 

 healthy branches were inoculated and placed under careful obser- 

 vation. The cause was ascertained to be a hitherto unknown, or 

 at least undescribed fungus, to which the name Diaporthe para- 

 sitica was given, in Torreya, 6: 189. Sept., 1906. 



This fungus is found to begin its destructive work beneath 

 the outer bark, in the inner layers and cambium, in which the 

 mycelium has its growth. The first indication of its presence is 

 the death of the bark, which changes in color on the exterior to a 

 pale brown. Later on, little yellowish pustules, containing the 

 spores, appear on the surface, giving a warty appearance to the 

 bark. These spores germinate throughout the summer and early 

 autumn and when ripe are disseminated by the wind and other 

 agencies; and those which find a suitable abiding place, in 

 abrasions of bark, or in wounds due to broken twigs and 

 branches, insect punctures, etc., immediately start new centers of 

 infection. The mycelium grows in a constantly enlarging circle 

 around the point of infection until it finally girdles the twig or 

 branch, cutting off the food and water supply and causing the 

 death of the member above. The destructive effects are there- 

 fore not due entirely to the attack of the fungus on the area im- 

 mediately infected but also to the incidental effect of the diseased 

 part in starving the part above. The smaller branches are there- 

 fore the most likely to go first and trees that are attacked gen- 

 erally present the characteristic feature of dead and dying 

 extremities for several seasons before they entirely succumb. 



Trees that are broken or trimmed or that otherwise present 

 numerous wounds or abrasions in which the spores may enter are 

 always the worst infected. In fact, so far as observations have 

 gone, it seems almost as if some injury were necessary for the 

 spore to gain entrance beneath the bark. The larger trees on our 

 hills, which were most affected by storms, were the first to go. 

 The larger proportion of these are already dead, while those of 

 smaller growth and with less injured branches, as the growth at 

 Tottenville, are mostly still living, although badly infected and 

 evidently destined to last but a few seasons more. 



