346 Bulletin 163. 



hyphae much larger in diameter than those previously mentioned. They 

 are closely septate, and constricted at the septa. Usually they branch 

 irregularly and profusely as in figure 52, but truly dichotomous branching 

 is often observed, and long moniliform chains of cells are not infrequent. 

 Such tufts of hyphae are also occasionally found on beets badly rotted in 

 the field. With age these chain-like aggregations break into hyphal 

 elements of a single cell or of several cells attached ; and most of these 

 cells may then function as conidia, producing on germination the charac- 

 teristic mycelium first mentioned. In the manner of germination these 

 cells are peculiar. The germ tube passes out through the septum origi- 

 nally separating the cell from its neighbor. As soon as the germ tube has 

 grown to an extent equal to several times the length of the parent cell, a 

 septum invariably forms at a short distance from the latter, the proxi- 

 mal cell is somewhat narrowed at its exit from the hyphal cell, and the first 

 septum decides the normal diameter of the tube. When germination takes 

 place from an inner one of several connected cells, a peculiar phenomenon 

 occurs. The germ tube may pass from one cell into and through its adjacent 

 neighboring cell ; and usually such cells through which germ tubes pass 

 seem to be themselves devoid of contents, or at least they lack the vacuolate 

 structure of the germinating cells. These characters are shown in figure 53. 

 When this fungus is grown on bean stems or on other nutrient media not 

 so rich as bean pods, crust-like sclerotial bodies are oftener formed. The 

 sclerotia begin as a closely branched mass of filamentous hyphae, and by 

 further growth these become so interwoven as to form a more or less com- 

 pact body. Sclerotia have been more readily produced by making fresh 

 cultures from pure cultures of the fungus which had been kept in the labor- 

 atory for a long time, the original cultures being made from damping off 

 lettuce. In all cases, however, the hyphae and the sclerotia are very dif- 

 ferent from those of Botrytis and other allied fungi often causing rots and 

 certain damping off diseases. 



e. The Beet Root-Rot Fungus as a cause of Other Types of Playit 



Diseases. 



While working with cotton diseases in Alabama in 1892, Pro- 

 fessor Geo. F. Atkinson found that the so-called "sore shin" of 

 seedling cotton plants is abundantly produced by sterile fungus. 

 Some of the results of this work were published in Bulletin 41 of 

 the Alabama Experiment Station. In his later work at this Ex- 

 periment Station upon damping off fungi, the same fungus was 

 again found to cause damping off of many seedlings, especially 

 of lettuce, cabbage, radish, egg-plant, &c. Under the caption 

 " Damping off by a Sterile Fungus," in Bulletin No. 94 of this 



