FusARiA OF Potatoes 



215 



common nor numerous when compared with all the other species of sec- 

 tion Elegans, usually only unicellular; aerial mycelium on hard agars 

 invariably well developed, of medium height (from 2 to 4 millimeters) 

 and density, very frequently forming macroscopically observable knots at 

 the hyphal tips, finally, if the conditions are right, resulting in production 

 of numerous small sporodochia; large (up to 12 millimeters in diameter), 

 bluish black, shiny, more or less wrinkled, sclerotia are frequently pro- 

 duced on potato tuber plugs; the sclerotia in some cases overgrown with 

 aerial mycelium, and then not so conspicuous; plectenchymic bodies 

 (from 1 to 3 or more millimeters in diameter) wartlike in appearance, 



Fig. 33. — Fusarium sclerotioides. a, Conidia from plectenchymic sporodochium from 14- 

 days-old culture on potato tuber plug; b, conidia from plectenchymic sporodochium from 58- 

 days-old culture on red raspberry cane plug; c, conidia from 24-days-old culture on slightly 

 acidified hard potato agar; d, sporodochial conidia from 6 -days-old culture, e, sporodochial 

 conidia from 12-days-old culture, f, sporodochial conidia from 51 -days-old culture, on hard 

 lima-bean agar; g, microconidia from 1 3-day s-old culture on hard lima-bean agar with 2 per 

 cent glucose; h, microconidia from aerial mycelium, i, sporodochial conidiophores, from 58-days- 

 old culture on red raspberry cane plug; J, conidiophoite from 6-days-old culture on hard lima- 

 bean agar; k, chlamydospores from 58-days-old culture on red raspberry cane plug 



white or pale flesh in color, often produced in considerable number and 

 in some cases finally bearing masses of septate conidia; conidia, however, 

 rarely produced on the sclerotia; color of the conidial mass somewhat 

 variable, but usually of a tint of pinkish buff; color of substratum varying 

 from nearly colorless when young to cinnamon red, deep vinaceous, and 

 dark vinaceous purple. (For typical color when mature see Plate i, 

 figure 12.) 



