50 ELEVENTH REPORT. 



To test the correctness of Aderhold's opinion I have made numerous 

 measurements of the conidia of the species of Sclerotinia found at Ann Arbor, 

 and a few measurements of the asci and ascospores in the apothecia of the 

 same species, partly from material sent to me by Prof. Dandeno of the 

 Michigan Agricultural College, and partly from material collected by myself 

 at Ann Arbor, on both peaches and plums. Many collections of the con- 

 idial stage have been made, and this form has been used for class work for 

 several years. 



As the result of the observations made on material from Michigan I have 

 reached the following conclusions: 



1. Only one species has come under my observation on the cultivated 

 fruits in this region. 



2. This species is exceedingly common on the stone fruits, plums, peaches, 

 and cherries, but is much less abundant on the pome fruits. I have found 

 it once causing a blight of young leaves and shoots of the Japan quince. 

 Pyrus japonica. Reade (1908) reports it on pomaceous fruits in New York, 



3. The size of the conidia (chlamydospores of some authors) is generally 

 smaller than the size usually given for Sclerotinia fructigena, hence they are 

 more nearly like those of Sclerotinia cinerea. 



4. The measurements of asci for Norton's Sclerotinia are far smaller than 

 those found in Michigan. 



5. There is some reason to believe that the species found here is the same 

 as the one found by Norton (1905) and named bj' him Sclerotinia fructigena. 



Reade (1908) obtained material directly from Norton and gives the size 

 of asci and ascospores nearly the same as those found by myself and also 

 the same as Aderhold described for Sclerotinia fructigena in Europe. In 

 that part of the world however this species is found mostly on pome fruits. 



The accompanying table shows the measurements of the asci, ascospores 

 and conidia as they have been reported by various people for the two species, 

 Sclerotinia fructigena and Sclerotinia cinerea. 



