Nov. is, i92o Sclerotinia minor, n. sp. 333 



description are from the combined data of the three years, since the 

 three sets of data agree very closely. Microconidia (fig. 1) have appeared 

 in abundance on a medium consisting of a 2 per cent agar flour in dis- 

 tilled water. Cultures have been obtained repeatedly from single asco- 

 spores which have shown the apothecia to be the fruiting stage of the 

 sclerotia-producing fungus. 



Smith (1900) 1 in studies of this fungus was unable to obtain apothe- 

 cia, although apothecia of S. libertiana were obtained in abundance. In 

 hundreds of cultures the fungus developed only the characteristic small 

 sclerotia, but in a single culture the small sclerotia at first appeared, and 

 later the characteristic large sclerotia of 5. libertiana appeared among 

 the small ones. Smith believed that 5. libertiana developed directly 

 from the small sclerotia and, therefore, concluded that the fungus is — 



a degenerate form of S. libertiana which has almost entirely lost the ability to repro 

 duce by spores. 



The repeated development during several years of characteristic 

 apothecia and the fact that during 10 years numerous cultures of sev-- 

 eral strains of the fungus have shown very uniform characteristics seem 

 sufficient grounds for considering the fungus a distinct species. As it 

 seems to agree with no described species, the following description is 

 given. 



Sclerotinia minor, n. sp. 



Apothecia one, rarely more, from a single sclerotium; disc saucer-shaped, 0.5 to 

 2 mm. in diameter; stalk cylindrical, slender, flexuous, attenuated downward, 5 to 

 12 mm. long; asci cylindrical to cylindro-clavate, 125 to 175 n by 8 to 11 m. average of 

 30 measurements 141 by 8.9 n; spores 8, ellipsoid to ovoid, hyaline, 5 to 8.8 /t by 8.3 

 to 19.9 n, average size of 200 spores 7 by 14. 1 n with over 80 per cent 6 to 8 ^ by 12 to 

 it n; paraph yses filiform to cylindro-clavate, septate, rarely branched, same length 

 as asci, 3 to 4 n in diameter; microconidia globose, hyaline, 3 to 4.2^, borne apically 

 on short obclavate conidiophores; appressoria abundant; sclerotia black, irregular, 

 0.5 to 2 mm. in diameter, often anastomosing to form irregular flattened bodies several 

 millimeters in length. 



Parasitic on lettuce (Lactuca sativa L.), celery (Apium graveokns L.), and other 

 plants; distribution, Massachusetts, New York, Pennsylvania, and Florida. 



SUMMARY 



Sclerotinia minor, n. sp., produces a decay of lettuce and other plants 

 similar to that produced by 5. libertiana. It is known to occur in Massa- 

 chusetts, New York, Pennsylvania, and Florida. 



1 Smith, Ralph E. op cit. 



