[Vol. 2 



418 



ANNALS OP THE MISSOURI BOTANICAL GARDEN 



first the mantle of mycelium, and then the cushions, so that 

 when the root is reduced to a mere shell there are only vestiges 

 of the cushions remaining. 



Sclerotia. — The true sclerotia are flattened or rounded 

 bodies varying in diameter from a few millimeters to several 

 centimeters. When mature they are of a deep violet-brown 



Fig. 3. Rhizoctonia Crocorum: 

 covering the surfaces of the large 

 "infection cushions." 



Cells characteristic of the tufted growth 

 sclerotia and to a certain extent of the 



darkening further in. 



Among the 



and are thickly clothed with a persistent velvety felt, ex- 

 ternally of the same color as the root-investing hyphae, but 



surface hyphae of the 

 sclerotia as well as of the " infection cushions" are found 

 chains of enlarged cells (fig. 3) quite distinct from the en- 

 larged cells of R. Solani. The sclerotia, as noted previously, 

 are always connected with the root felt by large hyphal 

 strands. In the saffron disease the sclerotia are formed both 

 in contact with the shriveling bulb and also in the adjacent 

 soil. On affected alfalfa roots they often occur below, and 



in the angles of, the larger branches, but often one finds no 

 sclerotia in immediate contact with the host. In connection 

 with diseased carrots, beets, and potatoes, they are not so 

 frequent, unless perhaps they are then formed at greater 



