8 THE PARASITIC FUNGI. 



parasites. ^ The former have their vegetative mycelium spread 

 over the surface of the host-plant, the latter penetrate into the 

 plant and there develop their mycelium. Both receive nourish- 

 ment from the cells of the host-plants, generally by means of 

 special absorptive organs inserted into the cells of the host, the 

 so-called haustoria. 



We may distinguish the following groups of parasites accord- 

 ing to the degree of their penetration into the organs of the 

 host-plant they attack : 



1. Epiphytes : (a) with haustoria which only sink into the 

 outer membranes of the host; 



(6) with haustoria penetrating into the cavity of the host- 

 cells. 



2. Endophytes : («) with a mycelium which grows in the 

 walls of the host-cell, and is generally nourished without the aid 

 of haustoria ; 



(6) with a mycelium which grows in the intercellular spaces 

 only, and is nourished with or without haustoria ; 



(c) with a mycelium which penetrates into tlie host-cells and 

 becomes an intracellular mycelium ; 



(d) lower fungi which live completely in a host-cell. 



1. Acquisition of nutriment by the epiphytic parasitic 

 fungi. The simplest mode of acquiring nutriment is found in 

 yeasts {Saccharomyces apieulatus, etc.) which frequent the outside 

 of living fruits, and live on the drops of sugary solution which 

 diffuse therefrom.^ 



^Epiphjrtic parasites always produce their reproductive organs outside their 

 host-plant. In the case of endophytic parasites, the reproductive organs of 

 some are produced inside the host-tissue, e.tj. the zygospores and oospores of 

 Ghytridiaceae and Peronosporeae, the chlamydospores of the Ustilagineae ; others 

 form their sporocarps wholly or partially embedded, the spores and conidia only 

 being discharged externally ; while a large number form sporocarps on the surface 

 after the epidermis has been torn. Conidia are generally abjointed from the 

 free surface of the host-plant. 



The terms epiphytic and endophytic parasites have been chosen with regard to 

 the development of the parasitic food-absorbing mycelium, tiome authors regard 

 epiphytism somewhat differently, and include amongst endophytes those forms 

 which live on the surface of the host and penetrate only by haustoria. If this be 

 accepted, epiphytism is very exceptional amongst parasites of the higher plants. 

 Zopf (" Die Pilze") gives as examples of this condition only the following : the 

 LaboiUbeniaceae inhalSiting the chitinous skeleton of certain insects, and Mdano- 

 spora parasitica on filaments of species of Isaria ; these have no communication 

 between the mycelium and their host. Species of Chaetocladium parasitic on fungi 

 and absorbing the cell-wall of the host at the point of contact, could, strictly 

 speaking, no longer be classed as epiphytes. 



^BiiBgen. " Ueber einige Eigenschaften d. Keimlinge parasitischer Pilze." 

 Botan. Zeitung, 189.3. 



