42 



Most fungous diseases have periods of quiescence alternating 

 witli periods of activity, depending largely upon varying weather 

 conditions. 



Also, there is reason to believe that the region covered by the 

 test is not now as free from the disease as Metcalf and Collins 

 think it is. Last summer there were found two centres of in- 

 fection previously overlooked.^ One of these consisting of a 

 gToup of six diseased trees, was within a few miles of Washing- 

 ton. In comi)any with Dr. Metcalf and others I had an op^ior- 

 tunity to examine these trees on December 30, 1911. One of 

 them, a tree over three feet in diameter, was in an advanced stage 

 of the disease. Large limbs ^^'ere dead and the lower portion of 

 the trunk was thickly covered witli spore masses of the fungus. 

 How long these trees had been aifected it was impossible to de- 

 termine, but it is safe to say that some of tliem liad been diseased 

 for at least a year and probably longer. That is to say, they be- 

 came infected in 1010 or earlier and must have been discharging 

 millions of spores at the very moment Dr. Metcalf was writing 

 his statement that the country' within a radius of 35 miles of 

 Washington was apparently free from the disease."* It is quite 

 ju'obable that other overlooked cases of the disease exist in the 

 vicinity of Washington at the present time. 



Further, We visited two places where diseased trees had been 

 removed and the disease "eliminated" in 1909. In one case, one 

 tree had been cut ; in the other case two trees. The bark had not 

 been removed from the stumps. On one stump Ave found a few 

 spore masses of the fungus; also on the base of a nearby tree. 

 On the other two stumps no fungus was found. The first-men- 

 tioned stump had not sprouted, but the other two Avere sur- 

 rounded by Ileal thy sprouts. At both points there were a few 

 chestnut trees in the immediate vicinity, but, so far as could 

 be determined, none of them Avere diseased. It should be stated, 

 hoAvever, that it is verA^ difficult to locate diseased trees in Avin- 

 ter. It is inevitable that the bark around the base of a diseased 

 tree and also the surrounding soil, fallen leaves and other litter 

 Avill become covered Avith spores carried down by rain. Hence, 

 when the diseased trees were removed thousands of spores were 

 left behind. How long such spores live and retain their power 

 of infection is not known. Now does it seem prol)able tliiit I Ik; 



