George Raymond Gage 29 



Similar experiments were conducted in which moisture was made the 

 limiting factor. Six petri dishes were prepared with dry filter-paper 

 linings. Spores and oats were introduced as in the previous experi- 

 ments. To the first dish no water was added ; to the second, one drop ; 

 to the third, three drops ; to the fourth, six drops ; to the fifth, nine 

 drops ; and to the sixth, twelve drops. The dishes were kept at a tem- 

 perature of 18° C. for ten days. At the end of this time they were ex-i 

 amined, and it was found that the spores had germinated in all dishes in 

 which three or more drops of water had been supplied. In the case of 

 the oats, only a few of those supplied with as many as twelve drops of 

 water showed any germination at all. It is evident from this that spores 

 are capable of germinating under moisture conditions Avhich are defi- 

 cient for the sprouting of the oat. 



These experiments were followed by similar ones in which the spores 

 Avere dusted directly upon the deglumed and the glumeless oat kernels. 

 With temperature as a limiting factor, it was found that at 6° C. not 

 only spore germination but also penetration of the pericarp epidermis 

 took place, while the oats failed to develop sprouts. With moisture as a 

 limiting factor, spore germination and penetration took place when 

 three or more drops of water were added to the petri dishes, but below 

 twelve drops the oats did not show any sign of germination. The 

 amount of pericarp penetration was much greater than with tempera- 

 ture as a limiting factor. 



From these data, it seems to the writer that one may be justified in 

 concluding that infection may take place in storage by spores which 

 reach the oats at threshing time. The ordinary manner in which oats 

 are usually stored would certainly supply the necessary conditions of 

 moisture and temperature. 



In those experiments whereby the writer determined the position and 

 the nature of the pathogene structures which carry the pathogene over 

 winter in the seed, some of the blossom-inoculated seed did not produce 

 plants with smutted heads. Examination of the culms of some of these 

 revealed the fact that mycelium was present in their lower parts. Seed- 

 ling invasion, then, had taken place, but for certain reasons the patho- 

 gene had not reached the inflorescence of the plant. This mycelium was 

 found in most cases to be confined to the first node, but in a few cases 

 it had reached the second and the third node. Since these oats were grown 

 under conditions most favorable for rapid germination and develop- 

 ment, it would seem that invasion of seedlings should universally result 

 from infected seed. The importance of this lies in the fact that smutted 

 panicles can no longer he considered as a criterion of infection, espe- 

 cially if variety tests are made in the field where absolute control of the 

 plants is impossible. There mighl easily exist non-inheritable differ- 



