Jan. 3,i 9 2i Fusarium-W ilt of Tobacco 523 



placed on the shade of the pigment given, because comparisons were not 

 made with Ridgeway's color standards and nomenclature at this time. 



Acid potato agar. — Good but rather light and "fluffy" aerial growth, 

 pure white, no agar coloration to a pale pink coloration, and formation 

 of blue-green sclerotial masses at margin of agar in older cultures. 



Potato plug. — Excellent growth, mycelium becoming faintly salmon- 

 colored and plug deep blue in parts; abundant formation of small bluish 

 black sclerotia in older cultures. 



Oatmeal agar. — Good growth, pale salmon-colored mycelium, medium 

 changing to pale lilac. Large sclerotial masses form at base of agar. 



Rice. — Good growth of white to pink mycelium. 



MELiLOTus stem. — Fair growth of white to pink mycelium. Sporo- 

 dochia formed abundantly after 15 to 30 days. Sporodochia forming 

 singly or in large masses. Pale to deep salmon in color. Abundant 

 production of small bluish black sclerotia. 



String-bean plug. — Excellent growth with production of lilac- 

 colored mycelium. 



Carrot plug. — Good growth with faint lilac coloration. 



Lima-bean agar. — Fair to poor growth only, hardly any pigment 

 production. 



Corn-meal agar. — Poor growth, practically no pigment production. 



Synthetic agar. — Good growth of white mycelium. 



Gelatin (BEEF). — Fair growth with some liquefaction. 



Tobacco agar (from green leaves). — Very poor growth. 



The cultural differences between the various strains of Fusarium 

 oxysporum used and those of the tobacco-wilt Fusarium are not believed 

 to be of sufficient importance to warrant presentation in detail, and only 

 the more striking differences will be mentioned. On cooked rice the 

 pigment of MacMillan's F. oxysporum was uniformly of a deeper color, 

 appearing usually as a blue violet to jasper red as compared with light or 

 shell pink with the tobacco- wilt Fusarium. The same was more or less 

 characteristic on oatmeal agar, while on the other media pigment differ- 

 ences were insignificant. A fairly striking difference appeared with 

 respect to the formation of sclerotial masses which came on early and 

 in abundance on potato plugs with the tobacco-wilt Fusarium but only 

 slowly or not at all with the F. oxysporum strains on hand. Sporo- 

 dochia were also produced in abundance with the tobacco-wilt Fusarium 

 on Melilotus stems but did not appear in any of the F. oxysporum strains, 

 although they had, no doubt, occurred previously in these strains. In 

 the absence of sporodochia in the cultures of F. oxysporum a satisfactory 

 detailed comparison from a morphological standpoint could not, of 

 course, be made. On the basis of certain morphological and cultural dif- 

 ferences — that is, pigmentation and sclerotial formation, together with the 

 failure to obtain wilt of the potato, it was at first believed that we were 



