DETAILED ACCOUNT OF SPJOCli'lC DISEASES OF PLANTS 507 



Wilt (Fseudomouas SkwaHl, Smith). — This is a specific communi- 

 cable disease of sweet corn and other races of maize, caused by a yellow, 

 polar-flagellate organism discovered in 1895 by F. C. Stewart. The 

 disease has been found on Long Island, in New Jersey, Washington, 

 D. C, Maryland, Michigan, Virginia and West Virginia. One of the 

 first signs of the disease in well-grown plants is the whitening (drying 



Fig. 181. — Germination of the chlamydospores of corn smut (Ustilago zece); i. 

 Various stages in germination from corn 3 days after being placed in water; 2, spores 

 germinated in contact with air; 3, several days after spores were placed in 1/20 per 

 cent, acetic acid, formation of infection threads, a. Spores; h, propiycelia; c, basidio- 

 spores; d, infection threads; e, detached pieces of mycelia. {After Bull. 57, Univ. 

 III. Agric. Exper. Stat., March, 1900.) 



out) of the male inflorescence. The leaves then dry out and the plant 

 is dwarfed, later the stem dries. If the leaves or the stem be chosen and 

 broken across, sHmy yellow contents ooze out. A cross-section of 

 the stem shows that the organism fills the vessels of the host plant and 

 the wilting is due to the stoppage of the water suppHes by the trachei'd 

 plugging. 



