698 . 



extends gradually over the whole tree. At the same time the foliage begins 

 to turn yellowish green in places and weakly pale shoots break out from the 

 bark. The foliage developed in the following spring appears yellow, or a 

 reddish green, the new shoots are stunted and their leaves roll and curl. At 

 times the tips of all the healthy, slender shoots suddenly show a continually 

 repeated formation of lateral axes which become weaker and weaker and 

 whole nests of sprouts are produced (usually in the autumn). Death occurs 

 sooner or later. In budding with healthy eyes from diseased trees, a large 

 percentage of the budded trees seems to be sick and, in fact, not only the 

 shoot developed from the eye itself, but also the stock, similar to the varie- 

 gation in albinism. 



The rosette, which occurs also in plums, was considered at first a 

 variety of the peach disease here described, but later Smith held it to be a 

 specific disease. Its course is uncommonly rapid, so that death occurs in 

 the same year, or, at the latest, in the following year. Here, too, the leaf 

 rosettes are produced by a strikingly abundant development of latent eyes 

 and the development of lateral shoots, which attain, however, scarcely one- 

 sixth the length of normal shoots. These may develop other side shoots, 

 which again branch. Such nests of branches often contain from 200 to 400 

 small leaflets and malformed stipules. At the bases of the shoots the leaves 

 are larger and better developed but peculiarly rolled in at the edges and 

 strikingly stiff, because of a certain rigidity of the mid-rib. These leaves 

 turn yellow in the early summer and drop. In the course of the summer 

 the rosettes dry up; the blossoms of the diseased shoots, however, do not 

 develop earlier than those of the healthy shoots, but rather somewhat later. 

 On the other hand, all the fruits which become gummy fall when still green 

 and never show the red specking as in peach yellows. In both diseases the 

 line, lateral roots are found to be shrivelled and dead and the rosette disease 

 is often accompanied by abundant gum centres. This rosette disease may 

 also be carried to the stock in budding. Only, as a rule, very many more 

 normal lateral eyes in a shoot develop into rosettes and, thereby, the bushy 

 formation becomes denser than in the peach yellows. 



Opinions as to the cause of this disease are divided, yet the bacterial 

 theory has become less prominent since it has been recognized that in many 

 cases mycelium and bacteria have not been found. For this reason the 

 theory has become much more universal that a constitutional disease is 

 concerned here, in which substances due to an abnormal metabolism may 

 be transmitted by grafting as in albinism and the mosaic disease. In fact, 

 here, the transmission probably takes place through the pollen, for Morse' 

 has observed that out of three varieties of peaches, two became diseased, 

 while the third, the white Magdalene, remained healthy. This variety could 

 not be crossed with others. 



1 Morse, E. W. On the power of some peach trees to resist the disease called 

 "yellows." Bull. Biissey Institution, Cambridge, 1901; cit. Ztntschr. f. Pflanzenkr. 

 1902, p. 58. 



