Fig. 5. A) Corn plant inoculated with Ustilago maydis by the hypodermic-syringe method; infection involving 

 almost the entire plant. B) Xaturallv infected plant, showing shoot and leaf infection (Stakman and Christensen, 

 311). 



becomes infected, the peduncle plus the tassel fre- 

 quently bends sideways. 



Ovaries are sometimes developed in the tassel of 

 corn and may produce normal seed. Some workers be- 

 lieve that smut infection in the tassel actually stimu- 

 lates the development of ovaries in the tassel. Thus. 

 it renders the tassel more subject to additional infec- 

 tion. Because of the similar phenomena in U. violiacae 

 (Pers.) Fckl.. this seems possible; but it has never been 

 substantiated experimentally (98). So-called tassel- 

 ears, common in certain selfed lines, are. in general, 

 very susceptible to smut infection. 



Young corn seedlings are very susceptible to smut 

 when injected with the smut organism. Seedling infec- 

 tion is usually expressed by severe hypertrophy of the 

 stem and leaves, conspicuous contortion, and eventual 

 death of the plant. One year, at St. Paul. Minn.. 1-2% 

 of corn seedlings in the field were killed by the smut 

 fungus (170). This was unusual, because smut galls 

 are seldom observed in the field on plants until they 

 are J^-l m tall. Since the galls produced on seedlings 

 or young plants are usually next to the ground where 

 it is moist, the smutty plants, especially infected seed- 



lings, disintegrate readily and thus may often be over- 

 looked (Fig. 6). 



litis ( 155). in 1910. reported an unusual overgrowth 

 of an infected ear. Virtually every kernel was trans- 

 formed into a long tube-like structure which terminated 

 in slender threads. This symptom would be akin to ear 

 infection caused by Sphacelotheca reiliana ( Ktihn ) 

 Clint. This species also attacks corn and some- 

 times spores of both species are found in the same 

 smut gall (139). It is possible that litis (155) was 

 dealing with S. reiliana rather than V. maydis. 



Several investigators (105. 158. 176) have found 

 that certain selfed lines of corn have a tendency to 

 become infected at definite sites on the plant, such as 

 the ear. shoot, neck, or tassel. In some selfed lines of 

 corn, nearly all the smut galls appear at the first node 

 nearest the ground line, in others at the neck of the 

 first node below the tassel, and in still others mostly 

 in the ear (157). Most lines of corn, however, have 

 generalized infection, resulting in galls that develop 

 on many different parts of the plant. The reason for 

 the specificity in location of the smut gall is not def- 

 initely known. Selfed lines of corn in the field react 



11 



