254 Plant Biology 



whose hyphae are septate and branched and break into numerous rec- 

 tangular or oval, thick-walled, infectious arthrospores. In lesions, how- 

 ever, C. immitis may appear as a spherical, thick-walled, nonbudding 

 structure filled with numerous small endospores which reproduce the 

 fungus within the tissues. (D) The pathogenic fungus (Sporotrichum 

 schenckii) (Fig. 74, D) causes a chronic infection known as sporotricho- 

 sis characterized by the formation (in skin, lymph nodes) of nodular 

 lesions which soften and break to form ulcers. The causal oroanism is 

 a fungus whose hyphae are septate and branched and bear oval or pyri- 

 form (pear-shaped) conidia laterally or in groups at the ends of the 

 lateral branches. (E) Several species of fungi, known collectively as 

 dermatophytes, produce infectious skin diseases known as dermatomy- 

 coses. The specific clinical symptoms and the causal organism vary with 

 the particular disease as shown by the following: (1) "Athlete's foot'' 

 (Tinea pedis, ringworm of the feet) is a world-wide infection of the skin 

 of the feet (especially soles and between toes) caused by such fungi as 

 Epidermophyton floccosum (Fig. 74, E) or various species of Tricho- 

 phyton (Fig. 74, F) . Epidermophyton hyphae bear the characteristic, 

 large, clavate (club-shaped), multiseptate conidia and Trichophyton 

 hyphae bear numerous, single-celled, thin-walled, oval or clavate conidia 

 (singly or in clusters). (2) Tinea corporis (ringworm of the body) is 

 an infection of the skin of the body caused by various species of the 

 fungi, Trichophyton (Fig. 74, F) or Microsporum (Fig. 74, G), and is 

 characterized by simple, or granulomatous lesions. Microsporum is com- 

 posed of hyphae with (a) large, multicellular, thick-walled, rough, 

 spindle-shaped macroconidia, and (b) small single-celled, clavate micro- 

 conidia borne on the sides of the hyphae. (3) Tinea capitis (ringworm 

 of the scalp) is a world-wide infection of the scalp and hair caused by 

 various species of fungi. Trichophyton (Fig. 74, F) or Microsporum 

 (Fig. 74, G), and is characterized by scaly, red lesions, and sometimes 

 deep ulcerative lesions. (F) The pathogenic fungi (Actinomyces hovis) 

 (Fig. 74, H) and several species of Nocardia cause a chronic, world-wide, 

 systemic infection called actinomycosis or lumpy jaw, and is character- 

 ized by granulomatous lesions tending to break down and form abscesses 

 which drain through multiple openings. The causal fungus, Actinomyces 

 hovis (Fig. 74, //), is anaerobic, closely related to the bacteria, and com- 

 posed of tangled masses of delicate, branching hyphae, while the species 

 of actinomycetes belonging to the genus Nocardia are aerobic and may 

 be inhaled with dust, straw, and other materials. 



