534 Journal of Agricultural Research voi. xn, Na^ 



and establishes the pathologic identity of the cotton- and okra-wilt 

 strains beyond reasonable doubt. 



Certain strains of the species of Fusarium causing cotton-wilt were 

 observed by WoUenweber (ji, 32) to produce an aromatic odor (lilac) 

 when cultured on starchy media such as rice; other strains less com- 

 monly isolated lacked this property. These latter strains were desig- 

 nated " F. vasinfectum var. inodoratum" by WoUenweber. As a further 

 indication of the identity of the species of Fusarium on okra with the 

 species of Fusarium on cotton, it should be noted that both the odor- 

 forming and the non-odor-forming strains have been isolated several 

 times from okra. While the ability to generate this odor is of doubtful 

 specific value, since other species of the section Elegans (WoUenweber, 

 32) possess this property, and this ability has been observed to be lost 

 in culture {Carpenter 7, p. 206), the fact that the species of Fusarium 

 from okra and cotton agree in this character is significant. 



Normal ^ cultures of this species of Fusarium develop in i to 3 weeks 

 at room temperature (PI. A). The best results are secured with plant 

 stems, potato cylinders, and other vegetable media. Morphologically 

 F. vasinfectum is scarcely distinguished from the other vascular parasites 

 of the section Elegans of this genus. 



Potato-cylinder cultures (PI. A) develop an ocherous-salmon-colored 

 pionnotes with 3- to 5-septate conidia (PI. 17, L-M). Blue-gray sclerotia, 

 similar to those of F. oxysporum Schlecht. (7, PI. A, i). are generally 

 present on this medium. The slight violet color of the upper part of the 

 pionnotes as represented in Plate A, 3, has never been seen in other 

 closely related species and is possibly of differential value. Stems of 

 Meliloius alba and Gossypium sp. are useful in developing the sporodochia, 

 which are likewise of an ocherous-salmon color. The plate of F. oxy- 

 sporum in an earlier paper (7, PL A, 2, 5) illustrates stem cultures of F. 

 vasinfectum equally well. On steamed-rice medium a more or less 

 brilliant red color soon appears, later becoming tinged with various 

 shades of purple and blue, especially in subdued light. Normal conidia 

 are not usually present in rice cultures, the value of this medium being 

 the color reaction and the formation of an aromatic substance with an 

 odor suggesting lilac (7, p. 206). Chlamydospores (PI, 17, I) are formed 

 in large numbers on this medium. 



The following measurements show the size and percentage of the 

 variously septate, normal, conidia (PI, 17, L, M) found in strains of F. 

 vasinfectum from okra and cotton : 



F. vasinfectum, strain 2709, isolated from okra. Culture, 27-day-old 

 stem of Melilotus alba, without pionnotes. Normal triseptate conidia, 

 60 per cent. Limits of size: 25.5 to 40.8 by 4.2 to 5.1 ju. Largest nor- 

 mal triseptate conidium, 40.8 by 5.1 ix.; smallest, 25.5 by 4.2 /i. Average 



' For a discussion of the idea "nonnal" and other special terms as used in relation to species of Fusarium, 

 see WoUenweber (jj, />. 255-257). 



