MORPHOLOGY OF THE GENUS ACTINOMYCES. P 



Charles Drechsler 



While the genus Actinomyces has received a large measure of 

 attention in its relations to soil biology and to human, animal, and 

 plant pathology, the natural affinities of the congeneric organisms 

 that it has been customary to include in the group have been the 

 subject of diverse opinions. Under a variety of synonyms, among 

 which Cladothnx, Nocardia, Discomyces, and Oospora have been 

 used nearly as frequently as Actinomyces, the group has been placed 

 with the bacteria, with the Hyphomycetes, or assigned to an 

 intermediate position. In the earher publications on the ray 

 fungus, including the papers by Bostroem (i)^ and by Wolff and 

 Israel (24), this organism was referred to the pleomorphic bacteria. 

 The belief was seriously entertained that cocci, bacteria, and spirilla 

 were produced by the plant, and in such regular succession that a 

 number of investigators were led to draw up detailed ontogenetic 

 schemes of considerable complexity. It is frequently not easy to 

 determine the exact nature of the structures that were interpreted 

 as pleomorphic stages. There are plenty of indications that con- 

 taminating bacteria were often present as secondary invaders; 

 but more frequently aerial spores, segments of spiral or sinuous 

 hyphae, and degenerative bodies of metachromatic substance were 

 mistaken for schizomycetous t>'pes of nearly every description. 



More recently Actinomyces has been frequently associated with 

 the tubercle and diphtheria organisms on the assumption that they 

 may represent a transition between the Hyphomycetes and the 

 true Schizomycetes. A family of Actinomycetes has thus been 

 erected as a natural group from these diverse components, united 

 chiefly by resemblances in their staining reactions, a usual or an 

 occasional filamentous habit, and the development' of clavate 

 elements in the animal body. It has been supposed by adherents 

 of such a taxonomic disposition that either a progressive phylogeny 



' Contribution from the Cryptogamic Laboratories of Harvard University, no. 83. 



» The bibliography will appear at the end of Part II, which will be printed in 

 February. 



^S] [Botanical Gazette, vol. 67 



