to 



MICHIGAN ACADEMY OF SCIENCE. 49 



siderable distance seemed to have lost a large proportion of their leaves. 

 Closer examination showed that many of their leaves had fallen to the ground, 

 and that many of the leaves still on the tree as well as many young shoots 

 were turning brown and dying. On the upper side of these dead and dying 

 leaves was observed a thin coating, ashy grey in color, appearing powdery 

 to the naked eye and with a hand lens. The appearance at once aroused 

 the suspicion of a Sclerotinia. This suspicion was the stronger because the 

 cultivated species of Prunus in this country are often badly attacked by the 

 brown rot fungus, commonly called Sclerotinia fructigena (Pers). 



Microscopical examination disclosed at once that the fungus was a species 

 of Sclerotinia, but not Scl. fructigena. It differed in two well-marked 

 characters from the corresponding stage of that species. The conidia were 

 considerably smaller, and were separated from each other by disjunctors, 

 a character possessed by Sclerotinia vaccinii Woronin, but not by Sclerotinia 

 fructigena. 



Attempts to identify the newly observed form with the conidial stage of 

 some known species were not successful. At the time the conidia were first 

 observed the socalled perfect form or ascus fruits were searched for, but 

 unsuccessfully. It was probably too late in the season, since at an earlier 

 date in that same year (April, 1905), Shimek and Seaver collected apothecia 

 growing from the l^uried seeds of Prunus serotina in the state of Iowa. Seaver 

 sent specimens of the apothecia to Dr. Rehm who described them as a new 

 species, Sclerotinia Seaveri (Ann. Myc. 3:519; 1905). Since Sclerotinia 

 Seaveri Rehm and the conidial form found by the writer at Ann Arbor 

 both grow on the same host, it is probable that they are different stages in 

 the life history of the same fungus. 



Reade (Ann. Myc. 6:112. 1908) has recently reported both the perfect and 

 conidial forms of Sclerotinia Seaveri as having been found at Ithaca, N. Y. 

 He describes the conidial stage (chlamydospores) as a new form, Monilia 

 Seaveri Reade, and as his chlamydospore stage is similar to what the writer 

 found at Ann Arbor and Dead Lake, Mich., 1905, this recently described 

 species is now known to occur in three different states, Iowa, Michigan and 

 New York. It may be a serious parasite since the trees first observed with 

 the disease at Ann Arbor were to a large extent defoliated. 



Reade gives the size of his chlamydospores (conidia) as 7-15, mostly 8-10 

 micromillimeters. As found by the writer they were mostly 7-10.8 x 6-9.6 

 micromillimeters, with a few large ones 12 x 12. The agreement is so close 

 that there is no doubt that they are the same species. 



The ascus fruitn were found at Ann Arbor, May, 1909. 



SCLEROTINIA FRUCTIGENA IN EUROPE AND AMERICA. 



Aderhold has suggested (1905) that in the United States the species of 

 Sclerotinia that commonly attacks the stone-fruits may be Sclerotinia cinerea 

 (Bon.) and not Sclerotinia fructigena (Pers.) as has generally been assumed. 

 He bases his opinion on the color of the conidial tufts as they are said to occur 

 on our stone-fruits, on the size of the conidia, and on the fact that in Europe 

 the Sclerotinia cinerea is the one which commonly occurs on the stone-fruits 

 and Sclerotinia fructigena is generally found on the pome fruits, such as 

 apples, pears and quinces, and lastly on the size of asci and ascospores as 

 found in apothecia which Norton (1902) was the first to discover and de- 

 scribe from material collected in Marvland. 



