DEATH OF CHESTNUTS AND OAKS. O 



by lightning this disease was found following up and enlarging the 

 wounds. Many of the white oaks killed by this fungus had been 

 blown down, In every case the upturned roots were covered with a 

 network of the black rhizomorphs (PI. II, fig. 1). Several groups of 

 two to four chestnut trees which had originated from sprouts around 

 a common stump vere found killed by this root-rot. Plate II, figure 

 2, shows two trees a'om a common base, one being already dead 

 and the other badly diseased. In the latter the bark and roots on 

 the side adjacent to the dead tree were killed for about one-third of 

 the distance around the base, and the rot had extended up the tree 

 8 feet under the bark. 



PERCENTAGE AND SIZE OF CHESTNUTS KILLED BY ARMILLARIA MELLEA. 



Of the 302 felled chestnut trees examined, 64, or 21 per cent, had 

 been killed by the Armillaria root-rot. The average diameter of these 

 killed trees was 12 inches; the largest chestnut killed was 26 inches 

 and the smallest 3 inches in diameter. Trees of all diameters be- 

 tween these limits were found diseased and killed. Of these trees, 

 10 had a diameter of 3 to 5 inches, 13 of 6 to 10 inches, 22 of 11 to 

 15 inches, and 19 of 16 to 26 inches. From this it follows that a 

 greater percentage of the large chestnut trees was killed by this root- 

 rot than of the smaller and younger trees. Of the 64 chestnut trees 

 killed, 41, or 64 per cent, were over 10 inches in diameter. The 

 average diameter of these 41 trees was 16 inches. In the white oak, 

 just the reverse occurred; a greater percentage of the smaller and 

 younger trees was killed than of the larger and older ones. 



PERCENTAGE AND SIZE OP OAKS KILLED BY ARMILLARIA MELLEA. 



Of the 477 oaks checked, 130, or 27 per cent, had been killed by 

 the Armillaria root-rot. The average diameter of these killed trees 

 was 7 inches, as compared with 12 inches in the chestnut. The 

 largest oak killed was 18 inches and the smallest 2 inches in diameter. 

 Trees of all sizes between these two extremes were affected. Of 

 these white oaks, 39 ranged in diameter from 2 to 5 inches, 70 from 6 to 

 10 inches, and 20 from 11 to 15 inches, with only 1 over 15 inches. 

 Of these 130 white oaks which had been killed, 84 per cent were less 

 than 11 inches in diameter and only 16 per cent were over 10 inches 

 in diameter, as compared with 64 per cent in the case of the dead 

 chestnut trees in the same locality. 



Of the white oaks killed by this root-rot, 46 had been overthrown 

 by the wind, while only 2 of the dead chestnuts had been blown 

 down. Of the wind-thrown oaks, 26 were from 6 to 8 inches in 

 diameter, showing that the smaller as well as the larger sizes of white 

 oaks were not as easily uprooted as those of medium diameter. 

 34907°— 14 2 



