CHAPTER III. 

 RELATION OF PARASITE TO SUBSTRATUM. 



!. EFFECT OF THE SUBSTRATUM ON THE DEVELOPMENT 



OF THE PARASITE. 



A NUMBER of parasitic fungi live only on one species of 

 host. For example ft-fi'mfinitt linrarwrn on Vmrln inm Jf /////// 1<*, 

 (/in <iliii-fi* on J'ii-i'H excelsa, 7V //<///"'//// /////< nlmni-inf on 

 nl iniii-ii<, Hi/xt' fiii'ni nerviseguium on Al>i>* jm-fin'ifd. 

 nnil i-ii/ii'iliii i GO. Andromeda inilijnlin. J)e llary 1 proposed 

 for cases like this the term monoxeny, while to cases in which a 

 parasite frequents several different species of host he -avr the 

 name polyxeny, or more particularly, dixeny, trixeny. etc. Ae 

 examples of polyxeny may he mentioned 111 ////>///" salicinum 

 f<mnd on all species of willow, and lUii/fixnm acerinum on the 

 genus AI-IT. Other parasitt-s attack not only different species 

 of some genus, but also different -vnera ; thus. /'////////" graminis 

 occurs on various cereals and grasses, 7V///Ay>////^/v/ omnivora 

 on many different plants, Phyllactinia .s////"////// on leaves ol' 

 ('(,,/////.-,-, Fn'jti*, and many oilier trees; r/"/-/V-y/.s y;///y;///-,v/ on a 

 l.i rue number of cereals and grasses, ('f/*tnji/i* riniiliilux on many 

 Cruciferae, and X"-tfi" i-iii/iii/nn-i/in on all kinds of broad-leaved 



trees. 



Monoxeny ;ind polyxeny must IM- carefully distinguished from 

 the aiitoccism and heteroecism of the rrt-diiifae. Many >pceir- 

 of ihis Liroup -o through their whole life-history, and produce 

 all their forms of spore on the same lio>t, others, however, pro- 

 duce some forni> of spore- spermatia and aecidio>pore> on one 



-t. and the remainder uiviln-p, ,ies and teleutOSpOieS OH 



,!, IstiT. p. -ill 



