Mar.4, i9i8 WUt Diseases of Okra 537 



seen in petri-dish cultures. The terminal branch is usually i to 3 times 

 longer than the virtel branches and measures from 1 5 to 60 ju. 



The mycelium is hyalin at first, becoming brownish with age. It is 

 septate, 2 to 4 jit in diameter, but is often swollen, all gradations from 

 slightly swollen threads to large, thick-walled, and knotted sclerotia, 

 and chlamydospore-like cells being present (PI. 17, G). The sclerotium 

 is at first but swollen, closely septate mycelium, which enlarges and 

 knots itself into a variety of forms. The measurements of sclerotia of 

 strains 1685, 1717, 2784, and 2985, recorded in Table I, were made only 

 from the more or less rounded aggregations. Such measurements of 

 irregular formations varying so greatly in size are only of general sig- 

 nificance. Certain strains of V. albo-atrum cultivated by the writer 

 produce sclerotia abundantly in a few days in petri-dish cultures. Macro- 

 scopically, their presence is manifested by a beautiful black zonation of 

 the colonies, as illustrated in Plate 19. In other strains, and sometimes 

 in other cultures of the same strain, these sclerotial rings either do not 

 develop at all or only after a long time ; yet these forms produce abun- 

 dant sclerotia if cultivated on potato cylinders and other vegetable media. 

 The entire growth then frequently consists of a black confluent layer of 

 sclerotia and hyphae. Parallel cultures of the same strain differ suffi- 

 ciently with respect to the characters of the conidiophores and sclerotia for- 

 mation so that specific determinations based on slight differences of these 

 characters and unsupported by inoculation tests are of doubtful value. 

 Verticillium albo-atnun Reinke and Berthold. 



Conidia ellipsoidal, iinicellular, 4.0 to 11. o by 1.7 to 4.2 ft, abscissed singly from 

 the sterigma tips of verticillate conidiophores. Primary whorls or virtels of branches, 

 I to 8 in number, 30 to 90 n apart, sometimes bearing secondar}- virtels. Branches 

 I to 7, usually 3 to 5 in number, 13 to 38 /x long, tapering, straight to slightly bowed. 

 Conidiophores 100 to 300 ^ or more in length. The terminal branch of the conidio- 

 phore is from 1 5 to 60 m long. Conidia may or may not collect in heads on the sterigma 

 tips. Mycelium septate, hyalin to brown with age; may become swollen into 

 chlamydospore-like chains of closely septate, knotted masses. These aggregates 

 constitute the sclerotia of this fungus. Vascular parasite, cause of a wilt disease of 

 okra, potato, eggplant, cotton, snapdragon, and probably of species of Abutilon and 

 Xanthium, ginseng, black raspberry, China aster, and dahlia. V. albo-airum may 

 prove to be the cause of the Verticillium-wilt disease reported on currants and goose- 

 berries by Aderhold (/). 



OCCURRENCE OF FUSARIUM VASINFECTUM .\ND VERTICILLIUM ALBO- 

 ATRUM IN WILT DISEASES. OF OKRA 



VerticUlium albo-atrum was found constantly inhabiting the vascular 

 system of wilt-diseased okra plants (PI. 27) in New Jersey, where this 

 crop is of considerable importance. This organism was also isolated from 

 similar material from Monetta, S. C, Birmingham, Ala., Middle River, 

 Cal., and Medford, Oreg., specimens from Middle River and Medford 

 having been collected by Dr. Wollenweber. 



On the other hand, a Fusariura indistinguishable from the cotton- 

 wilt Fusarium was constantly obtained from wilting okra collected at 



