THE FUNGUS BODY OF HYPHAL ELEMENTS. 43 



51. Parasites. — Especially is this true of tliose fungi wliich 

 grow in the interior of living organisms. The higher plants 

 are liable to be fastened upon by parasitic fungi, and com- 

 pelled to act as hosts to their unbidden and unwelcome guests. 

 Such a host plant may be entered when a mere seedling, in 

 which case the fungus grows with its growth, or it may not 

 be attacked until older or even mature. The host may be 

 permeated in all its jjarts by the fungus filaments ; or certain 

 members, only, such as the leaves, llower parts or twigs. 



Fig. 51. — Young hyphae of Exobasidium developinfr from spores, .r/, entering the 

 air-pores of the leaf of the cranberry. Others, fnjm j/', sj>'\ penetrate the skin 

 directly. Magnified about 600 diain, — After Woronin. 



may be affected. The effect of the fungus upon the host is 

 often scarcely visible to the unaided eye ; sometimes a 

 local disturbance is manifested bv swelling, unnatural color 

 or growth ;* sometimes the aflected members become dis- 

 torted and useless or are e\'en killed ; sometimes the disease 

 is general and is followed, slowly or quickly, by general 

 death of the host. 



52. Infection. — These internal parasites obtain entrance 



* See further IfH 222, 464. 



