The Sterile Fungus Rhizoctonia. 



61 



of a single cell or several cells in extent. The individual parts then 

 seem to function as conidia, and germinate within a few hours when 

 placed in suitable conditions. So far as observed, germination is 

 always by the protrusion of a tube through a septum. AYhen 

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

 and through its neighbor, as in Fig. 18, and thus peculiar appear- 

 ances may result. Some of the cells of the liyphal chain seem to be 

 devoid of protoplasm, and from neighboring protoplasmic cells the 

 germ tubes seem to pass into such empty cells as readily as directly 

 into the nutrient solution. When the germ tube is from lOfj. to 20/x 

 in length, it is invariably narrowed towards the outlet from the 



16. — The brown hi/phce which invest the cracks on diseased beets. 



parent cell, and a septum forms at a short distance from this outlet, 

 as in Fig. 18. Large, irregular, sclerotial bodies are sometimes found 

 upon the beet, but they are by no means of constant occurrence. 



If a part of a diseased beet is placed in a moist chamber, a loose 

 mycelial growth soon appears, and the threads may grow out to the 

 extent of half an inch or so. From this it is an easy matter to 

 obtain a pure culture by transferring some of this mycelium to 

 acidulated agar in petri dishes. The fungus grows readily upon 

 acidulated agar, while bacteria are for the most part excluded. The 

 fungus may then be transferred to bean pods, or beet plugs, in test 



