Diseases of the Sugar Beet. 345 



d. Special Characters of the Fiaigiis. 



The morphological characters of the fungus may well be studied both 

 from the mycelium found on the diseased beet, and from the growth in pure 

 cultures, secured as above mentioned. In pure cultures on bean pods and 

 on slices of sugar beet the fungus grows vigorously, and a loose mycelium 

 first appears. However the fungus may be grown, it shows a very charac- 

 teristic method of branching, which serves to identify it. In the young, 

 vigorously growing hyphae the branches are inclined at an angle more or 

 less acute with the direction of growth of the parent branch : and the point 

 of tmion of the two is marked by a slight constriction. Invariably the 

 branches are cut off by a septum at a distance of several micromillimeters 

 from the parent branch. At first the mycelium is quite hyaline, and 



52. — The large, closely septate hyphae which make up the short tufted growth. 



strongly vacuolate ; but with age the loose hyphae may become very light 

 brown in color. In the older hyphae of the loose growth it is noticeable 

 that the constrictions at the places of union of the branches are not so 

 evident, and this is especially true of the dark colored mycelium found 

 externally in connection with the diseased area of the beet root, as in figure 

 51, In the cultures the loose growth is followed by a closer tufted growth 

 of short hyphae. On such rich media as bean pods this close growth covers 

 almost the entire surface, and little tufts may also appear on the glass of 

 the test tube. This growth is at first somewhat mealy in appearance, but 

 later it becomes deep brown in color. These tufts are made up of short 



