478 



MICRO-ORGANISMS AND DISEASE [chap. 



spores are formed by endogenous formation. When these 

 sporangia are cylindrical or club-shaped, they include eight 

 spores, and are called asd : the spores being ascospores. All 

 conidia or spores by germination grow into the mycelial 

 threads which become septate or subdivided into a row of 

 cylindrical cells ; these by division cause the lengthening of 

 the mycelial threads. 



Fig. i8g. — Oidium Lactis. 

 Mycelium and spores. 



{a) Oidium lactis. — Here the mycelium is composed of 

 septate branched filaments of various thicknesses. Some 

 branches of the mycelium at their ends or laterally at a sep- 

 tum produce by division a series of spherical or oval conidia- 

 spores, about o-ooy to o-oi mm. long. These ultimately 

 become isolated, and then germinate into a short cylindrical 



