FUNGI 137 



The Thallophyta are plants in which there is no differentiation be- 

 tween root and stem. 



The classes of Thallophyta which are of interest medically are i. the 

 Algae and 2. the Fungi. 



The Algae contain chlorophyll. An exception to this is with the Schizophyta, 

 algae which include the Bacteriaceae or Schizomycetes and the Schizophycese or 

 Cyanophyceae. The bacteria do not contain chlorophyll and the Cyanophycese 

 or blue-green algae contain a blue pigment (phycocyanin) in addition to chlorophyll. 

 It is in their relation to bacteria that algae are important. Some authorities consider 

 the family Bacteriaceae as belonging to the order Cyanophyceae. 



Diseases caused by fungi are known as mycoses. 



Some include Lichenes as a separate class. These are really sym- 

 biotic organisms Fungi parasitic on Algae. 



The fungi do not possess chlorophyll. They are in their simplest forms ramifying 

 filaments called hyphae. The vegetative hyphae which intertwine in tangled threads, 

 as a support, are termed the mycelium, while those which project upward are called 

 the aerial hyphae and are the ones which bear the conidia or spores. 



The aerial hypha which carries the fruiting organ encasing the conidia (sporan- 

 gium) is called the sporangiophore and the more or less rounded termination of this 

 hypha, which projects into the sporangium, is called the columella. 



The hypha may be composed of one cell or of many cells separated by septa 

 (septate). 



The orders of the class Fungi which are of interest medically are: 

 i. the Phy corny cetes; 2. the Ascomycetes; 3. the Hyphomycetes. 



Phycomycetes. These produce a copious network-like mycelium, which is non- 

 septate, and reproduce asexually by means of a sporangium, a case-like structure 

 borne on the clubbed extremity of an erect hypha (columella) and containing numer- 

 ous spores or, as in the case of the suborder Oomycetes, reproduction is by heter- 

 ogamy. (Dissimilar sexual cells a smaller male, antheridium, and a larger female, 

 oogonium. By fertilization by antherozoids from the antheridium penetrating the 

 oosphere we have oospores.) 



The suborder Zygomycetes reproduces either asexually (a sporangium filled with 

 spores) or by isogamy (two similar but sexually differentiated cells conjugate and 

 form on fusion a zygospore). 



Belonging to this suborder we have four families, only one of which, the Mucor- 

 acidae, is of importance medically. In this family we have three genera: Mucor, 

 without rhizoids; Rhhopus, with rhizoids and unb ranched aerial hyphae and, 

 Rhizomucor, with rhizoids and ramified mycelium. 



Under anaerobic conditions the non-septate mycelium of these fungi may break up 

 into short septa resembling yeasts. 



Two species of Mucor are of pathogenic importance. 



