HELOTIACEAE 261 



that conidial stages alone are known in some species, as in Monilia 

 laxa (probably M. cinerea of Europe), occurring on cherries in 

 the Pacific Northwest. Similarly detached conidial forms of 

 Botrytis exist, such as B. cinerea, one form of which was recently 

 found by Groves and Drayton (1939) to have a Sclerotinia stage. 



Among the better-known species usually placed in Sclerotinia 

 are 5. jnicticola on stone fruits, S". jnictigena on pome fruits (not 

 known to occur in North America), S. rtcini on castor bean 

 {Riciniis connmmis), S. inimla on Vaccinium vitis-idaea, S. scle- 

 rotionmi on lettuce, cucumber, potato, and various other garden 

 plants, and S. heteroica on Ledum paliistre and V accinhim uligi- 

 7? o Sinn. 



Honey (1928) created the name Monilinia for the monilioid 

 species of Sclerotinia, with S. jnicticola as the type. The tax- 

 onomy of this organism has been greatly confused, a subject dis- 

 cussed in detail by Roberts and Dunegan (1924, 1927). Its dis- 

 comycetous stage, which matures on mummified fruits lying 

 partly buried on the ground during the period when the flower 

 buds are opening, was first described as Ciboria in 1883 but was 

 rediscovered in 1902, when it was thought to be identical with 

 S. jnictigena. Other names applied to it include S. cinerea and 

 S. americana. 



Sclerotinia {Monilinia) jnicticola is most widely known in its 

 conidial or Monilia stage as it occurs on decaying plums and 

 peaches. From the mycelium within the fruits are produced 

 grayish tufts of hyphal branches, which extend through the 

 cuticle. These tufts are conidiophores that form chains of lemon- 

 shaped or moniliform conidia. When the end walls between co- 

 nidia are first formed, they are plane, and the cells are then barrel- 

 shaped. Later the septa split into two layers, and a fusiform plug 

 is formed between the tAvo layers. This plug, the disjunctor, 

 serves to detach the conidia from each other. While the dis- 

 junctor is forming, the conidia increase in size, become lemon- 

 shaped, and are then easily dislodged to inoculate other fruits. 



When the fruits have decayed and have fallen to the ground, 

 they become mummified. Within the mummified tissues, apo- 

 thecial stromata are produced throughout the summer and the 

 succeeding fall and winter. In the spring brownish apothecia, 1 

 to 1.5 cm broad, with stipes 1 to 10 cm long, emerge from the 



