iQig] DRECHSLER— ACTINOMYCES 163 



9. As in the vegetative thallus, metachromatic granules occur 

 in the aerial mycelium, being very rarely found in the spores or 

 sporogenous hj-phae, but becoming very abundant in degenerate 

 sterile hyphae. 



10. The older axial filaments of some species show marked 

 distensions which, in extreme cases, result in figures simulating 

 Leptomitus. These arise as local distensions at the points of attach- 

 ment of the more extensive lateral sporogenous processes. Cuneate 

 modifications of the sterile axial filaments below the origins of 

 branches also occur. 



1 1 . Curious spherical structures appear regularly in some forms, 

 both in the sterile axial hyphae, where they may contain either a 

 median septum or a number of peripheral metachromatic granules, 

 and in the sporogenous h}T)hae, where they are associated with the 

 regularly spaced septa. 



12. The spores germinate readily in suitable solutions, producing 

 1-4 germ tubes, the approximate number being more or less char- 

 acteristic of the species. 



13. Owing to the absence of any well defined bacterial character- 

 istics, the writer is of the opinion that the view that Actinomyces 

 represents a transition between the Hyphomycetes and the Schizo- 

 mycetes, as well as the phylogenetic corollary based upon it, may 

 safely be abandoned. If mere size is to be regarded as important, 

 it would appear to be equally profitable to look for bacterial 

 affinities in some ascomycetous and sphaeropsideaceous forms, 

 the hyphae of which are similarly very minute. It is doubtful 

 whether far-reaching taxonomic generalizations can be based on the 

 "acid-fast'' staining reaction, especially as this reaction has not 

 played a very important role in mycological research. There 

 seems to be no adequate reason why the genus should not be classed 

 in an unqualified manner with the Hyphomycetes, as a mucedineous 

 group with tendencies toward an erect Isarioid habit. 



The writer wishes to acknowledge his indebtedness to Professor 

 R. Thaxter, under whose direction this work was done; to Pro- 

 fessor W. G. Farlow for the use of books; and to Professor B. 

 Fink for samples of soil collected on the islands of Porto Rico and 



