30 Journal of Agricultural Research vol. xx, No. i 



standing plants even in the worst- infected portions of the field never 

 exceeded 15 per cent, while in the lodged portions of the field the head 

 infection was, in some small areas, as high as 100 per cent. Considering 

 that the field was not over two acres in extent, that the inoculum of 

 Gibberella saubinetii, which was responsible for over 90 per cent of the 

 infections in this field, was very uniformly distributed throughout the 

 field, and that there were no other explanations for this great difference 

 in degree of infection between the lodged and the standing plants, the 

 effect of lodging on the prevalence of headblight infection becomes more 

 striking. 



VARIETIES IN RELATION TO THE DISEASE 



During the summer of 191 8 more than 30 varieties of wheat, both 

 winter and spring, were grown by the Department of Agronomy, Uni- 

 versity of Wisconsin, on the University farm, and all were attacked 

 more or less by headblight. There was marked difference between 

 them in the degree of infection, but no variety was entirely free. As 

 will be seen from the list given in Table II, among the varieties ex- 

 amined were representatives of types having very different morpho- 

 logical characters, from those which have very fine and succulent chaff 

 to those which have hairy or very hard chaff. 



Since the winter varieties examined were badly winter-killed, no 

 significant count could be taken which would indicate their relative 

 susceptibility to headblight. The spring varieties, on the other hand, 

 were in very good condition and uniform throughout the series of plots. 



The 15 spring-wheat varieties were sown in small plots of the same 

 size, the plots being in one series which extended across the whole field. 

 The whole series of varieties was repeated so that the variety planted 

 on the first plot was repeated on the sixteenth plot, the variety planted 

 on the second plot was repeated on the seventeenth plot, and so on. 

 The plants in each plot were examined carefully and the blighted heads 

 counted. The number of blighted heads of each variety in the two 

 series was in many cases exactly the same. If there was a difference, 

 it did not amount to more than two or three heads. The results are 

 given in Table II. 



These results, while not convincing, are very interesting, especially 

 when we consider that all plots had the same preparation and cultivation, 

 the same preceding crop, were on the same piece of land, that all varieties, 

 while not in exactly the same stage of development, were in a stage in 

 which they were susceptible to blight, and that the degree of infection of 

 a certain variety was the same in the two series located a considerable 

 distance apart. 



One may suspect that the relative amount of infection of the seed used 

 for sowing is the cause both of the difference of infection between 

 different varieties and of the uniformity in degree of infection of the same 



