248 PRINCIPLES OF SOIL MICROBIOLOGY 



Absidia (Nos. 86-87, PI. XIII). This 

 genus is fairly well represented in the soil, 

 although not very common; 12 species of 

 Absidia have been described by Lendner. 

 A number of species have been isolated by 

 Hagem (A. orchidis, A. glauca, A. spinosa). 

 Other species have been isolated by Oude- 

 mans and Koning, Dale, Waksman and 

 others. 

 2". No stolons are formed by the mycelium. 



(a) Heterothallic, occasionally homothallic, but, 



in the latter case, the zygophores generally 

 arise from comparatively distant parts of 

 the mycelium, never formed between 

 branches of a single aerial hypha, and are 

 usually equal. Mucor (Nos. 91-92, PI. 

 XIII). This genus is one of the most 

 common in the soil and is the largest in 

 the number of species found in the soil. 

 It has been studied in detail by Lendner, 

 Hagem, Povah, Jensen and others, several 

 of whom having isolated some 25-30 species 

 from different soils, in different parts of 

 the world. 



(b) Homothallic zygospores produced early and 



abundantly. Zygophores arise close to- 

 gether, always originating from a single 

 aerial hypha; they are usually unequal. 

 Zygorhynchus (No. 90, PI. XIII). This 

 genus is represented in the soil only by two 

 species, 64 but these are among the very 

 few most common soil fungi. They have 

 been isolated by Hagem, Namyslowski, 

 Jensen, and have been found in every soil 

 examined from all parts of the world. 

 They are found especially in sandy sub- 

 soils poor in organic matter. 

 2'. Sporangia similar to those of the Mucoraceae, but of two 

 kinds: one kind is multispored, the membrane breaking 

 up, leaving only a naked columella; the other kind of 

 sporangia (sporangioles) contains few spores, which 

 have persistent membranes and are often without colu- 

 mellae. They are disposed at the extremity of branched 

 sporangiophores, which are themselves arranged at 

 regular intervals on the principal sporangiophore. 



64 Namyslowski, B. Zygorrhynchus Vuilleminii, une nouvelle Mucorinee 

 isol£e du sol et cultivee. Ann. Mycol., 8: 152-155. 1910. 



