100 Rbport of the Botanist of xhb 



European species. Nothing will at present be said of the limita- 

 tions or identity of species. The latter is a matter which must 

 be determined largely by cross inoculations, together with mor- 

 phological studies. Inoculation experiments have been in prog- 

 ress for two years, but they are not yet in shape to be fully 

 reported; hence a presentation of the results will be deferred. 

 RJiizoctonia is a form genus established to include certain 

 sterile fungi occurring upon the roots of plants. The members 

 of this genus, however, may be readily located by certain dis- 

 tinguishing characters of the mycelium. In pure culture, more- 

 over, a very characteristic form of growth is to be found. The 

 young hyphae growing in diseased tissue or in pure culture show 

 a distinctive manner of branching; but as this character is in 

 general the same for all, a description of the beet fungus will 

 suffice for this account. The young branches are inclined to the 

 direction of growth of the parent branch at an angle more or less 

 acute. And the former are somewhat narrowed or constricted 

 where united with the latter, as in Fig. 1. At a distance of a 

 few microns from these places of union, a septum is invariably 

 formed. The young hyphae are often strongly vacuolate; but 

 later they usually become uniformly granular and more deeply 

 colored. The branching also seems to have occurred more nearly 

 at right angles to the main hypha, and the constriction at the 

 place of union may not be so marked. (See Fig. 2.) On the beet 

 root a short, tufted, or somewhat sporodochia-like growth of the 

 mycelium may also occur. The hyphse of these tufts are brown, 

 closely septate, constricted at the septa, and often branching 

 in an irregular or dichotomous fashion, as in Fig. 3. Such hyphae 

 may eventually break up into hyphal lengths of a single cell or 

 several cells in extent. The individual parts then seem to func- 

 tion as conidia, and germinate within a few hours when placed 

 in suitable conditions. So far as observed, germination is al- 

 ways by the protrusion of a tube through a septum. When sev- 

 eral cells are connected, a germ tube from one cell may pass into 

 and through its neighbor, as in Fig. 4, and thus peculiar appear- 

 ances may result. Some of the cells of the hyphal chains seem 



