12 BULLETIN 395, U. S. DEPARTMENT OF AGRICULTURE. 



fungus with Cladosporium carpopJiilum Thiim. from peacli fruit from 

 America, h,e found only minor morphological differences, but obtained 

 inconclusive results from cross-inoculation experiments. Though 

 he does not formally conclude that these organisms are specifically 

 identical, he expresses the personal conviction (1901, p. 657) that they 

 are "ein und denselben Pilz" and calls attention to the fact that 

 Pammel (1895, p. 207) and Selby (1897, p. 118) considered Clado- 

 sporiums associated with cherry and plum scab in America to be 

 Clados'porium carfOfMlum Thiim. If Aderhold were correct in his 

 belief, it would foUow that Cladosporium carpofhilum Thiim. should 

 become a synonym of Cladosporium cerasi (E,bh.) Aderh., which in 

 turn the same investigator (1900, p. 544) considers to be the im- 

 perfect stage of Venturia cerasi Aderh. The data which have been 

 presented, however, fail to convince the writer that the organisms 

 in question are identical. Therefore, until further evidence is 

 adduced^ he accepts the name Cladosporium carpopTiilum Thiim. 

 for the peach-scab parasite. 



While the contributions which have been made to the knowledge 

 of Cladosporium carpopTiilum since Von Thiimen's (1879) description 

 make desirable certain further emendations, it is the behef of the 

 writer that, in order to avoid unnecessary taxonomic comphcations, 

 these should not be made until the relationships of the Cladosporiums 

 on the stone fruits have been further determined. Meanwhile, Von 

 Thiimen's (1879, p. 13) description, which is quoted below, is in most 

 essentials clear-cut and accurate. 



CI. maculas orbiculares, saepe confiuentes, viridi-nigricantes, amiiilatas formans; 

 hypMa brevibus, erectis, flexuosulis, continuis vel interdum septatis, subramosia, 

 tenuibus, 4 mm. crassis, fuscis; sporis fusoideo-ovatis, utrinque obtusiusculis vel raro 

 vertice subacutatis, rectis, non vel obscure uniseptatis, diapbanis, 20 mm. long., 5-6 

 mm. crass., dilute fuscescentibus. — Thiimen. 1. c. emend. 



In Persicae vulgaris Mill, fructibus maturis, epidemice. — Austria inferior (Thiimen). 



MORPHOLOGY. 



Mycelium. — The morphological characters of the mycehum vary 

 much with conditions. The very young hyphse are dehcate, hyaline, 

 branched, and septate. As the fungus develops, however, the 

 diameter of individual ceUs normally increases, transverse and, more 

 rarely, longitudinal divisions occur, and the walls of the more ex- 

 posed cells thicken and become ohvaceous. On the fruit lesions this 

 growth may give rise to pseudoparenchymatous fungal masses, while 

 a like development may occur beneath the cuticle of the twigs (figs. 

 2 and 4). In culture, stromateoid masses develop (PI. Ill, fig. 3), 

 the individual cells becoming much enlarged and often rounded, 

 giving an in'egularly moniliform appearance to the mycehal threads. 

 In old cultures the mycelium tends to break up into its component 

 cells, which under favorable conditions are capable of putting out 

 vifforous hvnhfR. In all of thpspi sfromflfp'nirl .^tTiip.tnrps tbp, Wfllls of 



