73 

 ments that the poa species are infected only temporaXily by various 

 biologio races of Claviceps. 



It is further interesting to note that Brachypodium 

 s^ly^itic-uffi , the only real host of this form, flowers iriuch later 

 than the fungal ascospores are produced, and that direct infection 

 is impossihle. The fungus has been forced, therefore, to acTaipt itself 

 to another host vihich is found usually in association vdth the first 

 r.nd vAiich flov/ers just about the time of ascospore production. This 

 is ^ili"uin e ffusum. Miliuin effusum is in blossom about the end of May 

 and at the same time the ascospores are discharged from the perithecia. 

 These spores germinate, establish themselves ve.y easily on M. effusum 

 and produce an abundant ?.nd long-period secretion of honey dew. 

 Sclerotia are not formed, however on Milium effusum , or only very 

 seldom, nnd such, when occurring, are only rudimentary. 



Meanwhile, the B. silvaticum sends out its flavers v>hich can 

 easily be infected with the conidia produced on M. effusum . Then 

 numerous sclerotia are formed. There are necessary, therefore, for 

 the full development of the ftmgus, under normal conditions, two host 

 plants; BrachvT30dium silvaticum and Milium effusum . For this phenomenon 

 v;e find an analogy in Sclerotinia ledi . 



As is Imown, Woronin described for the first time (1896) 

 an Ascongroetous form with heteroeceous habit ( Sclerotinia ledi. ) 

 At the tiHB of ascospore ripening of this fungus the host Ledum is 

 not yet developed. The spores infect first Vaccinium uliginosum which 

 is in proper stage of development at that time and from the latter 

 the fungus passes to its true host. 



