46 PEACH ROSETTE. 



more than two seasons. Such a thing as the lingering on of a diseased 

 tree from year to year, as in peach yellows, is not known. I have seen 

 trees completely diseased in June and dead in November, which first 

 showed symptoms in early spring and were in apparently perfect health 

 the preceding autumn. This is the common course of the disease. 



When a tree is attacked in part, the shoot-axes and foliage of the 

 remaining limbs often appear to be perfectly healthy, but these limbs 

 always develop rosettes, and die the following year. Not infrequently 

 I have observed the disease to progress gradually from the affected side 

 to the healthy, i. e., the parts on the healthy side first to be attacked 

 being the bases of the limbs. The bark of trunk and limbs on affected 

 trees presents no peculiar or symptomatic differences. Undoubtedly 

 there are changes in the cambium cylinder corresponding to the short- 

 ening of the terminal shoot-axes, but these are not visible externally. 



The following are some of the more noticible symptoms : 



(a) Young shoot-axes. Commonly the disease first appears in the un- 

 folding shoot-axes, i. e., in early spring when the buds first open. In 

 healthy trees only a small proportion of the winter buds develop into 

 branches. The rest die or remain dormant. In this disease a very large 

 part of the winter buds grow into shoot-axes and also a very considera- 

 ble number of dormant buds on the older and larger branches. The 

 shoot-axes in healthy trees, especially the terminal ones, generally attain 

 a growth of 6 to 20 inches and develop ten to_twenty vigorous leaves 

 with dormant blossom and foliage buds in their axils. As the season 

 advances such shoots ripen their wood, cast their foliage, and remain 

 quiescent until spring invites the opening of their buds and the re- 

 newal of vegetative activity. In diseased trees, the shoot-axes push 

 only 1 to 3 inches, lose, almost completely, the ability to develop and 

 ripen wood, and to form dormant buds. The buds on such shoots grow 

 as soon as they are formed, or rather, as soon as they receive the initial 

 differentiation, developing into diminutive soft branches, which fre- 

 quently branch again, but never attain any good degree of size, vig- 

 or, or maturity. It is ordinary to find 15 to 30 primary branches and 

 often some additional secondary ones, on a shoot-axis less than 3 

 inches long, and not over one-eighth inch in diameter at its base. The 

 tendency of this effort of branching is from below upward, i e., the 

 oldest and largest branches are near the base of the shoot, but almost 

 always not quite from the base, the buds remaining undeveloped in 

 some of the lowest leaf axils. 



(b) The foliage. The leaves on these dwarfed branching shoot-axes 

 are multiplied correspondingly, and the result is compact tufts or 

 rosettes containing 200 to 400 diminutive leaves, and many additional 

 green stipules which are frequently misshappen and abnormal. The 

 older and larger leaves near the base of the shoot frequently reach a 

 length of several inches and are characterized by a very pronounced 

 inrolling of the margins of the leaf, and by a certain stiffness due to a 

 peculiar straightening of the midrib. These leaves turn yellow in early 



