18 



MEDICAL MYCOLOGY 



over its whole surface. Small mycelial branches, which serve to attach the 

 mycelium to the substrate and to absorb the nutrients, have become special- 

 ized in form and function in several groups. When the absorbing organs are 

 rootlike, filamentous, finely branched and tapering, they are called rhizoids 

 (frequent in the Chytridiales). When they are intracellular, clavate, bluntly 

 lobed, coarsely branched or coralloid organs of parasites which do not imme- 

 diately injure or kill the host cell, they are referred to as haustoria (frequent 



Fig-. 1. — Hypnospore formation in 1 ; 2, Mucor racemosus; S, M. dimorphosporus ; i, Rhizopnis 



arrhisus. (After Lendner 1908.) 



in plant parasites). When the function seems to be purely one of attachment 

 and the mycelial branches are flattened and disciform, bluntly lobed or 

 branched, or even coarsely filamentous, they are called holdfasts (e.g., Bhizopus 

 of the Mucorales). Appressoria are holdfasts which are superficial or non- 

 penetrating, although they may be intercellular (frequent in the sooty molds). 

 In many cases, the hyphae grow together in groups, intertwine, adhere, and 

 form a thick tissue, called plectenchyma. If the single hyphal elements are 



