PEZIZALES 



325 



the obligate manner we shall find in the Uredinales. While in the latter 

 the host change is connected with a change of nuclear phase, is condi- 

 tioned in its rhythm by plasmogamy and meiosis, and, besides, usually 

 takes place between two hosts far removed systematically; in Sclerotinia 

 and Claviceps we are dealing with plurivorous forms which have been 

 specialized on seasonal hosts. 



The economically important representatives of the subgenus Eusclero- 

 tinia, as S. Fuckeliana, S. Libertiana, S. Trifoliorum and the various 

 Sclerotinias on monocotyledonous bulbs, in their choice of hosts are much 

 less specialized than those of the subgenus Stromatinia. Thus, S. 

 Fuckeliana is parasitic on the Vine, Ribes, turnips, etc., S. Libertiana on all 

 sorts of cultivated garden vegetables and *S. Trifoliorum on alfalfa, 



Fig. 215. — Sclerotinia sclerotiorum. 1. Conidial stage. Botrytis cinerea. 2. Appressorium. 

 3. Diagrammatic cross section of apothecium. (After R. E. Smith, 1900.) 



Onobrychis sativa, clover, etc. During the summer, they kill the infected 

 organs, developing in them the sclerotia in which they overwinter. Their 

 conidia arise singly on characteristically formed conidiophores (Fig. 215, 

 1) and hence, in contrast to those of Stromatinia, are placed in Botrytis 

 rather than in Monilia. As the cultural determination of the perfect 

 form is rarely possible, one generally places them, especially those of the 

 S. Fuckeliana and S. Libertiana groups, in the collective species Botrytis 

 cinerea. Thus one provisionally names all entirely or hemiparasitic 

 pathogens which probably belong in the life cycle of a Sclerotinia. 



Kharbush, (1927) reports the usual nuclear phenomena in the devel- 

 opment of the ascogenous hyphae and asci in Sclerotinia Fuckeliana. 



Geoglossaceae. — While in the Mollisiaceae and Helotiaceae the 

 fructifications have the typical apothecial structure, in the last family of 

 the Inoperculatae, the Geoglossaceae, there appears a fundamental 



