ORDER MONILIALES (hYPHOMYCETEAE) 585 



Chapter 11 under the Saccharomycetales. Many of the asporogenous 

 yeasts are truly Fungi Imperfecti, in that the ascogenous stage is un- 

 known. The plant-inhabiting species of Oospora such as 0. nicotianae 

 Splend. & Sacc. are probably not at all closely related to 0. lactis, but 

 since we are dealing with form genera the matter is not so important 

 unless good characters can be discovered that will permit the rather un- 

 wieldy genus to be broken up into several smaller genera. 



The genus Actinomyces, in the older, wider sense of the name, repre- 

 sents beyond doubt a series of several closely related genera whose 

 relationships within the fungi are not agreed upon by various investi- 

 gators. The mycelium consists of branching, rarely septate hyphae of 

 great slenderness, approximately 1 m in thickness or more or less. These 

 may be aerobic or almost anaerobic in their mode of growth. The hyphae 

 submerged in the substratum eventually break up, by the formation of 

 numerous septa, into short, cylindrical spores. In the genus Streptomyces 

 there is formed a mat of external, branched, aerial conidiophores which 

 become septate basipetally into conidia which eventually break apart and 

 are oval or cylindrical or eUipsoidal. These germinate by 1 to 4 germ 

 tubes. The conidiophores are more often spirally wound. The presence of 

 true nuclei (Drechsler, 1919 and Newcomer and KenKnight, 1939) and 

 this mode of germination by germ tubes seem to justify Drechsler and 

 some other students in considering these genera as true fungi. Until more 

 is known as to any perfect stage they may well be placed in the Moni- 

 liaceae near Oospora. Perhaps Drechsler (1935a) is right in drawing atten- 

 tion to the close similarity of the vegetative structures and asexual mode 

 of reproduction between Streptomyces and some of the Zoopagaceae in 

 the Phycomycetes. 



Waksman and Henrici (1943) place the genera related to Actinomyces 

 in two families, which they unite with the Mycobacteriaceae in a separate 

 order the Actinomycetales, locating it in a position intermediate between 

 the Bacteria and the Fungi Imperfecti. These two families are the Actino- 

 mycetaceae, with no aerial conidia, and with two genera Actinomyces, 

 anaerobic, and Nocardia (syn. Proactinomyces) , aerobic, and Strepto- 

 mycetaceae, with aerial conidia, in chains in Streptomyces and singly at 

 the tips of upright conidiophores in Micromonospora. The chief species of 

 Actinomyces is A. bovis Harz, the organism causing the disease of animals 

 (especially cattle) known as "lumpy jaw." The genus Streptomyces con- 

 tains many soil inhabitants feeding upon dead vegetable matter. S. scabies 

 (Thaxt.) Waks. & Henrici is one of the organisms causing the scab of 

 potato tubers and other subterranean organs of living plants. For the use 

 of Streptomyces sp. in the production of antibiotics, see p. 603. 



In Cephalosporium (Hyalosporae) the conidiophores produce the 

 spherical or ellipsoidal conidia successively at the apex, each new conid- 



