24 



Journal of Agricultural Research 



Vol. XX, No. i 



15 per cent. Good, healthy, plump seed may show no decrease in 

 germination, while weak and shriveled seed may show considerable 

 decrease in germination. 



Gibberella saubinetii, besides preventing some of the seeds from germi- 

 nating, attacked from 10 to 40 per cent of the young seedlings, causing 

 rotting and browning of their roots, bases, and sheaths (PI. 3, A). A 

 number of the plants so attacked, usually few under normal conditions, 

 rot and die before reaching the surface of the soil. Others wilt and die 

 after reaching the surface, while the large majority recover almost 

 entirely and attain practically normal development. Over 20 spring- 

 wheat plants which showed marked rotting and browning of the roots 

 and bases caused by this organism while they were grown on sterilized 

 soil from infected seed in pots out of doors, when transplanted to the 

 pathological garden recovered rapidly and reached full development, 

 producing heads as normal as those on the control plants. Only 2 of the 

 plants so transplanted wilted shortly after the transplanting, and the 

 writer is inclined to attribute the wilting more to the transplanting than 

 to the parasitism of the organism. This fact shows that, although G. 

 saubinetii when present on the seed will infect many of the seedlings, it is 

 not able to injure them materially unless the plants are growing under 

 extremely unfavorable conditions, as was the case with the plants shown 

 in Plate 2, B. In this case, the experiment was conducted during Febru- 

 ary, 191 8, at a time when there was a minimum of sunlight in the green- 

 house and when all the greenhouse plants were consequently weakened. 

 The results of the experiment are summarized in Table I. 



Table I. — Average results of two inoculation experiments on each of 2 "wheat samples, 

 sample I consisting of hand-picked, healthy, plump kernels, and sample 2 consisting of 

 hand-picked, healthy, but average kernels sown May 23, 1919, in pots kept out of doors 



Sample 

 No. 



Number of kernels. 



Germina- 

 tion. 



Number of 

 healthy- 

 plants. 



Number of 



plants 



showing 



rotting 



of 



roots and 



bases. 



Number of 

 killed 

 plants. 



/Control, 100. . . 

 \ Inoculated , 100 

 j Control, 100. . . 

 \ Inoculated, 100 



Per cent. 



90 

 76 

 69 



89 



75 

 7i 



4? 



IS 



5 



27 



While it was shown by numerous experiments that Gibberella saubinetii 

 is able to decrease the percentage of germination of wheat, rye, barley, 

 and oats and to cause rotting and browning of the roots and bases of some 

 of the seedlings and even to cause wilting and dying of others, it was also 

 noticed that this varied considerably from time to time and that some 

 factors like light, temperature, moisture, and soil conditions have much 

 to do with the degree and severity of infection. 



