CHARACTERISTICS OF THE DISEASE. 15 



V and vi. Plate v is from a Michigan tree, and is very unusually tufted. 

 Plate vi, No. 1, is the ordinary Delaware form; while No. 2 of the 

 same plate is an appearance common in late autumn. In Delaware and 

 Maryland these last were more than usually abundant in the tops of 

 vigorous trees in the summer and autumn of 1890. 



So much concerning the characteristics of the disease. Now, in con- 

 clusion, some words upon its progress. 



Gradually or simultaneously, as the case may be, all of the limbs de- 

 velop the same symptoms. Consequently, the tree falls into a decline 

 and finally dies. Trees once attacked rarely, if ever, recover. This 

 statement is still in dispute, but I feel quite sure. Hundreds of yel- 

 lowed and decaying orchards on the upper part of the Chesapeake and 

 Delaware peninsula bear witness every day to the truth of this asser- 

 tion. In a very few instances I have had trees pointed out to me as 

 once diseased and now recovered, but no such cases have ever come 

 under nay own observation. Always such trees have shown symptoms 

 of disease later on, or else there was some uncertainty connected with 

 the original diagnosis of the case (p. 30), 



The duration of the disease varies greatly. If the symptoms progress 

 slowly from limb to limb, the tree may live a long time. If the whole 

 tree is speedily involved, decay and death are correspondingly rapid. 

 I have known trees to die at the end of the first season, but such is not 

 usually the case. In Maryland and Delaware, as well as in regions 

 farther north, the affected trees generally live from two to five years, 

 and possibly longer in some cases. Incidentally I am keeping watch 

 of several hundred trees to determine this point more accurately. The 

 trees are worthless from the start and should be removed as soon as 

 the disease appears. If allowed to remain, complete death occurs, very 

 frequently, the third or fourth year, the last feeble sign of vitality 

 being a few yellowish tufts on the trunk or some of the limbs (plate 

 Vila). The tree shown in plate vnfr was attacked in the spring of 1887, 

 when it was 5 years old, i. e,, set 5 years. At that time the tree was 

 remarkably vigorous and handsome. It died in the summer of 1890, 

 i. 6., about 3| years from the time it first developed symptoms, but its 

 foliage was yellowish the second year, and vegetation during the last 

 year of its life was very scanty and feeble, being confined principally 

 to branching sprouts on the bases of the larger limbs. 



Generally speaking, the longer the disease has prevailed unmolested 

 in any locality the greater is the number of cases annually, and the less 

 is the probability of getting trees up to bearing age before they are 

 attacked. This peculiar and interesting fact has been observed repeat- 

 edly in Connecticut, New York, New Jersey, Maryland, Delaware, and 

 Michigan. 



