186 FUNGOUS DISEASES OF PLANTS 



k Of the twenty-five genera of this family, the genus Sclerotinia 

 includes the most important parasitic species. It is characterized 

 particularly by the fact that typically the fruit body arises from a 

 sclerotium, which may be defined as a compact mass of hyphal ele- 

 ments, sometimes distinctly pseudoparenchymatous or sclerotial in 

 texture, serving commonly as a resting or more resistant mycelial 

 stage. The sclerotium may be developed upon the living host or it 

 may form after the death of the diseased structure. The apothe- 

 cium is usually borne in this case on a rather long stalk, and it is 

 smooth and more or less brown in color. The cylindrical asci 

 bear in uniseriate fashion eight usually elliptical spores. Conidial 

 and chlamydosporic stages may be present. 



VI. SCLEROTINIA 



DE BARY, A. Ueber einige Sclerotinien und Sclerotinienkrankheiten. Bot. 



Zeitg. 44: 377-38? (et seq.). 1886. 

 WAKKER, J. H. Ueber die Infection der Nahrpflanzen durch parasitische 



Peziza- (Sclerotinia-) arten. Bot. Centrbl. 29 : 309-313,342-346. 1887. 

 WORONIN, M. Ueber die Sclerotienkrankheiten der Vaccinieen-Beeren. Mem. 



de 1'Acad. imp. de Sci. de St. Petersbourg 36 (se'r. 8): 1888. 



Many species of Sclerotinia produce diseases of plants, and 

 although several species have been carefully studied, there is 

 much in the way of unconfirmed data. A monographic study 

 of the genus is greatly needed. The apothecial or perfect stage 

 is not developed, as a rule, until the mycelium, or a sclerotium, 

 has undergone a period of rest. In several cases it is well estab- 

 lished that the conidial stages are members of the form genus 

 Monilia. It is also declared that other species include Botrytis 

 forms in their life cycles. For convenience the following tentative 

 classification of species of Sclerotinia is suggested : 



1. Species comprising in their life cycle not only apothecia, but also a 

 Monilia stage, that is, with conidia produced in chains, the latter frequently 

 separated one from another by special structural devices. 



a. Species in which both spore forms may be produced upon the same host ; 

 such as Sclerotinia fructigena, S. Vaccinii, S. Aucuparice, S. baccaruin, S. 

 megalospora, and S. Oxycocci. 



b. Species whose life cycles are not complete upon a single host ; Sclerotinia 

 heteroica and S. Rhododendri. 



2. Species which may embrace a form of Botrytis as a conidial stage ; 

 Sclerotinia Fuckeliana. 



3. Species in which no conidial stages have been convincingly demon- 

 strated ; Sclerotinia Libertiana, S. Betula, and S. Trifoliorum. 



