CLASSIFICATION OF PARASITES AND SAPROPHYTES. 7 



as liemi-parasites. They must, however, be iiichided amongst 

 the hemi-saprophytes, because doubtless they are capable of 

 going through their whole development as saprophytes. The 

 hemi-parasites include, amongst others, the Ustilagineae, all of 

 which live for a time as parasites, and cannot, even by artificial 

 cultivation, be made to complete their life-history as saprophytes. 

 While, however, many of the Ustilagineae are adapted to a com- 

 pletely parasitic life, others can, in the form of sprouting conidia, 

 live and multiply saprophytically. The conidia of Bxobasidiimi 

 and Exoascus continue to bud off conidia for a considerable time 

 in nutritive solutions, yet in nature, the spores probably produce 

 infecting hyphae at once, and the fungus is but little suited to 

 sustain a saprophytic mode of life. Phytophthora infcstans is 

 more easily reared as a saprophyte, and occurs in nature as such, 

 hence it approaches somewhat towards tlie hemi-saprophytes. 



True Parasites. 



The Uredineae may be taken as the most typical of the true 

 parasites ; they constantly pass through their whole life-history 

 on living plants, and cannot be cultivated on a dead substratum. 

 So also the Erysipheae, although frequently their spores only 

 reach maturity on a dead substratum, as do also those of 

 Ehytmna and Polystigma. Ergot of grain and the Sclerotinia 

 inhabiting berries, are also truly parasitic, even though their 

 apothecia or perithecia are produced from hibernating sclerotia, 

 and though their conidia can be saprophytically cultivated on 

 dead pabulum. 



The Peronosporeae and Protomyces are also true parasites. 

 In many other forms the development of germ-tubes, or the 

 sprouting of conidia, may be obtained in artificial nutritive 

 solutions by exclusion of rival fungi and bacteria, yet it is 

 doubtful whether this takes place in nature. 



§ 3. MODE OF LIFE OF THE PAEASITIC FUNGI. 



The parasitic fungi may be divided according to the place of 

 their occurrence and their mode of attack on the host, into two 

 categories, which may be designated epiphytic and endophytic 



