M(iDE OF LIFE OF THK 1'AKASITKJ Fl'M.I. 



I can however hardly regard as parasites, fungi like tln-e 

 which live on an accidental outflow from plants or plant-cells, 

 veil though they regularly frequent places where an outflow is 

 to be expected. They exert no influence on the host-plant, 

 and they are nourished by substances which can no longer he 

 regarded as belonging to the host. I would rather include 

 them amongst non-parasitic epiphytes which, without specially 

 adapting themselves, settle on any part of a living plant win-re 

 sugary solutions suitable for their nutriment may occur. < >ne 

 might imagine however such epiphytes inducing a diffusion of 

 nutritive substance from the cells of the host-epidermis to the 

 closely adherent fungal hyphae ; then we should have tin- 

 simplest mode of parasitic acquisition of nutriment on the part 

 of epiphytes. They would take up food-material from the epi- 

 dermal cells in much the same manner as many intercellular 

 hyphae do from the adjoining walls of the host-cell. 1 



Kpiphytic parasites frequenting the surface of plant-organs 

 generally endeavour to increase their supply of nutriment from 

 the host-cells by formation of haustoria, which pierce the cuticle 

 or the whole cell-wall. Biisgen has shown experimentally 

 that the adhesive discs, often formed on the germination of a 

 spore, owe their origin to a contact-stimulus; the formation and 

 direction of the infecting hyphae, on the other hand, though 

 depending on this, are much more determined by a stiinulus 

 originating from the host-cell itself. In this we have a confirma- 

 tion of the accuracy of our definition of 

 parasite and saprophyte. 



The appressoria, adhesion-organs or 

 adhe-ivc discs just mentioned, are char- 

 acteristic of many parasites. They are 

 foriin-d chiefly on epiphytic mycelia, 

 but also accompany the earlier life of 

 other fungi. In the case "f epiph\t<-s, 



pores are furined on definite places of 



. ' I 10. 1. /-. S]M,I, ,.f /: ., r / t ,ttf. 



such an adhe81Ve-dl8C, and from (These umbttt\ germinating on tlu- 



. . Ill 11- ' 1 ' 1 ' 1 ' ""'" "' :l I '" M I 1 '-" 1 ' : '" "' 



haUStOna are developed, or a hVPha is healon-dlscandhavutoriumhHVi 



I..H1K-.I. i.\' ry.) 



given oti and enters the host-plant to 



form a mycelium. The appressoria of the Ki \-ipheac ale \.T\ 

 characteristic; in many they arc broad Inbed di>-- ( |-'i-. li; in 



' < 'nm|i;ir- I ' para -ilf- un In-i-. I - a ml t un^'i all v.ul\ _M\ i-n, p. B (HOt( 



r\ 



