18 USTILAGO AVEXAE AND USTILAGO LEVIS 



3. Swedish Select inoculated at blossoming time, glumes removed and 



therefore mycelium in the pericarp only i possibly some unger- 

 minated spores present ) . 



4. Swedish Select dusted with spores at harvest time, and therefore 



with ungerminated spores on the outside of the glumes. 



5. Swedish Select dusted with spores after removal of glumes, and 



therefore with spores on the pericarp only. 



6. Selection 202 (glumeless) uninoculated. 



7. Selection 202 inoculated at blossoming time, and therefore with 



mycelium in the pericarp (possibly some ungerminated spores 

 present). 



8. Selection 202 dusted with spores after harvest, and therefore with 



ungerminated spores on the pericarp. 



Vstilago levis. — In a like manner, lots of oats were obtained together 

 with a supply of U. levis spores. Prior to inoculation the spores were ex- 

 amined as to their smooth-spored character. It may be well to note, 

 however, that in obtaining spores for inoculating the first normal blos- 

 soms to appear, it was necessary to break open the smut sori. These cov- 

 ered sori do not open naturally until about the time when the last blos- 

 soms (largely from lateral shoots) are maturing. In the case of late- 

 appearing smutted heads, the sori were not open at harvest time, and 

 were broken open only by threshing. The possibility, then, of such 

 spores entering the flowers lies in the fact that some of the first spores 

 to mature are disseminated and lodge in the last of the flowers to open. 

 Microscopic examinations following inoculation of flowers with U. levis 

 spores disclosed germination and penetration of the floral organs identi- 

 cal with that described above for U. avenue. With glumeless oats the 

 spores can, of course, come in contact with the caryopsis after pollina- 

 tion, or even during threshing. These points are discussed in more detail 

 later. 



The following seed supplies were obtained: 



1. Swedish Select (glumed) uninoculated. 



2. Swedish Select inoculated at blossoming time, glumes not removed 



and therefore with mycelium developed in the floral parts (pos- 

 sibly some ungerminated spores present). 



3. Swedish Select inoculated at blossoming time, glumes removed 



and therefore mycelium in the pericarp only (possibly some 

 ungerminated spores present). 



4. Swedish Select dusted with spores at harvest time, and therefore 



with ungerminated spores on the outside of the glumes. 



5. Swedish Select dusted with spores after removal of glumes, and 



therefore with spores on the pericarp only. 

 -6. Selection 202 (glumeless) uninoculated. 



