14 Journal of Agricultural Research vol. xx.no. i 



week, while the second lot showed ioo per cent severe infection and 

 the third lot remained free from the disease until full maturity. Some 

 of the plants in the first lot showed slight infection seven days from the 

 time of inoculation, during the time when they were in blossom. These 

 results show that the spores remain on the infected heads until the 

 heads reach a susceptible stage before infection takes place. 



SOURCE OF NATURAL INFECTION 



An important source of infection is the seed used for sowing. Cereal 

 seeds carry, externally, viable conidia of Gibberella saubinetii, as well as 

 of Fusarium spp., and many of the kernels are internally infected with 

 these fungi, as has been shown by Selby (9), Selby and Manns (u), 

 Schaffnit (<?), Bolley (1), Wollenweber (12), Naumov (5), and many 

 others. Many times the writer isolated G. saubinetii and several 

 Fusarium species from what seemed fairly normal wheat, barley, rye, 

 and oat kernels, as well as from kernels from blighted heads of the same 

 crops. In all cases G. saubinetii was the organism most commonly 

 isolated. Seed so infected carries the organism to the soil, where it 

 attacks the young seedlings if conditions are favorable. It passes the 

 winter in the soil, preferably on the killed seedlings or other organic 

 matter. In the spring it resumes its growth, producing new conidia 

 which when carried to other parts of the plant cause head or node 

 infection. 



The perfect stage of this organism, which is formed in abundance on 

 infected heads, straw, or cornstalks, is an important source of natural 

 infection. The conidia of this organism, which are always produced in 

 abundance on the infected heads and stems, are the chief, if not the only, 

 source of secondary infection. 



Whether Gibberella saubinetii, as well as the other Fusarium species 

 attacking the cereal crops, is present in the soil at all times and for long 

 periods of time, always ready to attack the susceptible hosts sown 

 on such soils, is an important phase of this problem to which the writer 

 has given no attention. 



OVERWINTERING OF THE FUNGUS 



The organism, because of its comparative resistance to cold and drying, 

 overwinters in various ways. When introduced into the soil with the 

 winter crops, it overwinters in the form of mycelium and conidia where 

 these are formed on the killed seedlings and on other organic substances. 

 It also overwinters in the form of mycelium in and on the seed, straw, 

 heads, and cornstalks that have been infected with the fungus the 

 summer before. The organism has been isolated from such plant parts 

 kept out of doors throughout the winter and spring. During the winter 



