108 MASSACHUSETTS HORTICULTURAL, SOCIETY. 



niunber of fungi Avhicli we know in the perfect form is very 

 large, even in some of the genera which have been shown to be 

 the perfect stage of some of tliese imperfect fungi, and also that 

 some of these are even to be connected with others of the imper- 

 fect fungi if we could only be fortunate enough to trace out their 

 life history. But many of them are found under conditions 

 which would probably preclude their being connected with any 

 but a few of the known species of the imperfect fungi, unless 

 the j)henomenon of heteroecism (growing on different hosts 

 during different stages) has a very much wider application in 

 nature than there has as yet been any hint of from authentic 

 sources. One well-authenticated case of heteroecism outside of 

 the Uredineae is found in the species of Sclerotinia, known as S. 

 ledi Xawascliin, which has been found by Woronin and Xawas- 

 chin to have its conidial form on Vaccinium uliginosum, while the 

 sclerotinia form is developed on Ledum jialustre. 



In many of these imperfect forms there is a sort of physiologi- 

 cal dimorphism existing between the parasitic imperfect form, as 

 we have seen, which grows on the living parts of the host, and 

 the perfect form, which we have seen grows on the dead parts of 

 the same host. It appears as a parasite in one case and as a 

 saprophyte in the other. This property of growing as a sapro- 

 phyte suggests that in some cases the perfect form may grow and 

 produce its fruit on other material than that of the same host on 

 which the imperfect form may develop, since in artificial cultures 

 many of these fungi will grow well on several different sub- 

 stances, which in one sense would be a sort of heteroecism. In 

 other cases it is equally probable that the perfect form, even as a 

 saprophyte, does not depart widely from the path of its host in 

 its development. 



One very interesting and important peculiarity lies in the fact 

 that in many of the fungi belonging to the great group which we 

 now have under consideration, each of the complemental forms 

 may develop and multiply quite independently of each other. 

 We have seen how by the intervention of stroniatic bodies or 

 sclerotia, or even by the conidia themselves, imperfect forms may 

 live through the winter or during other unfavorable periods for 

 their development and may start the disease and the course of 

 their development entirely independently of the perfect form; 

 or the mycelium may live in the adjacent tissues of the diseased 



