70 ' BOTANICAL GAZETTE [january 



occurrence here, as everywhere else, is an indication of advanced 

 degeneration. In the more mature mycelium of Actinomyces 

 VIII (fig. 47) metachromatic granules are usually very conspicuous, 

 often occupying most of the space in the narrowed constrictions 

 between the large vacuoles in the highly inflated mycelial segments. 

 The appearance of such a thallus is not in the least suggestive of the 

 structure of bacteria, and indicates that the resemblance between 

 Actinomyces and the true Schizomycetes in the consistency of proto- 

 plasm, emphasized by some writers as an important phylogenetic 

 connection, has been unduly overestimated. 



While the sterile filaments in the nutrient and in the aerial 

 mycelium are relatively uniform in structure throughout the genus, 

 the sporogenous apparatus of many species exhibits a large degree 

 of morphological individuality. This diversity has not usually 

 been recognized by writers, and has undoubtedly been responsible 

 for a portion of the controversy that has arisen, particularly with 

 regard to the method of spore formation. Lachner-Sandoval (12) , 

 from a study of Actinomyces albido-flava, distinguished two kinds of 

 propagative bodies: (i) fragmentation spores appearing as spheri- 

 cal to cylindrical segments in old hyphae, formed by a contraction 

 of the protoplasm; and (2) segmentation spores developed by a 

 septation of the tips of aerial filaments. Segmentation was usually 

 found to involve only lateral branches coming from aerial hyphae, 

 but in submerged growths it frequently extended also to the main 

 filament, leading to the development of a dendroidic system of spore 

 chains. Lachner-Sandoval's figures of these formations, how- 

 ever, are much less striking than might be expected from the 

 description in the text, and do not convey the impression of rami- 

 fications approaching treelike proportions. 



Neukirch identified the segmentation of Lachner-Sandoval 

 with oidium-spore formation among the fungi, and abandoned the 

 use of a specific term. He vigorously disputed the development of 

 aerial spores by a septation of the mycelium. According to his 

 account the spores are formed as the result of successive contrac- 

 tions of protoplasm until approximately isodiametric portions are 

 separated by regularly alternating empty spaces. This process he 

 identified with the fragmentation of Mace, locahzing it in a differ- 



