32 PEACH LEAF CUKLI ITS NATURE AND TREATMENT. 



a. The development of the hyineniuin occurs only in the floral leaves of the host 

 plant. Three species. 



J>. The development of the hymenium occurs only upon the foliage leaves. Ten 

 species. 



c. The resting mycelium extends intercellularly in the deformations of the leaves. 

 One species. 



It nia}^ be seen under A h of this arrangement that Exoaseus defor- 

 mans is said to possess perennial mycelium, inhabiting- the inner tis- 

 sues of the axial organs, and that the development of the hymenium 

 occurs only in the foliage leaves of the host plant. As will be seen in 

 another part of this })ulletin, it is perhaps a perennial nature of the 

 mycelium of E. deformans which makes it difficult to thoroughly rid 

 an orchard of curl bv means of spra}^ treatment, but this matter 

 requires further careful consideration. 



The synonym}^ of Exoascus deformans (Berk.) Fuckel has been 



given b}^ numerous writers. Sadebeck^ gives it as follows: 



Ascomyces deformans Berk. Intro, to Cryptogamic Botany, 1857, p. 284. 



Ascosporium deformans Berk. Outlines, 1860, p. 449. 



Taphrina deformans Tu\. Ann. Sci. Xat., 1866, Y. Ser., t. r>., p. 128. 



Exoascus deformans Fucl^el. (o) Pers/ca' Fuck. Symbolaj Micolog., 1869, p. 252. 



This fungus has been very commonly observed and frequently 

 described by botanists since Berkeley called attention to it in 1857. 

 It has thus been known as the cause of curl for a little less than half 

 a century. The peculiar behavior of peach foliage under its action 

 has been observed by horticulturists, however, for a much longer 

 time. The disease was well described in England in the earl}" part of 

 the present centur}'. 



In spite of the ver}' common appearance of Exoascus deformans 

 upon peach foliage in peach-growing countries, the descriptive litera- 

 ture relating to its life history is not free from conflicting statements. 

 Several species of Exoascem have been confounded with this species 

 in some instances, and subsequent writers have perpetuated the 

 confusion. 



Some earlier writers believed this species inhabits a considerable 

 number of host plants, thus resulting in the description and distribu- 

 tion of several distinct species as Exoascus deformans. To avoid such 

 confusion it would be best to confine remarks upon this species to the 

 fungus as it develops upon the peach {Prunus ]:>erslca L.), which if 

 not its only host, is certainly its most common one. 



At least two modes of infection of the peach tree by Exoascus 

 deformans are said to exist — (1) by means of perennial mj^celium, 

 and (2) by means of the spores of the fungus. 



Sadebeck^ is authority for the statement that the mycelium winters 

 over in the youngest portions of the one-j^ear-old branches of the host 



'Sadelieck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, p. 53. 

 ''■ Idem, 1. c. 



