36 



gations, fluctuating as yet in their results, have not been worked out sufficiently. They will he 

 reported in a statistical survey in the next work on smut fungi. 



To determine the influence of temperature, experiments were made on the germinating 

 capacity of smut spores and seed grains at constant low temperatures. It was proved that smut 

 spores can germinate in nutrient solution almost at the point of freezing. Germination is thus 

 only relatively delayed, otherwise it is just like that at higher temperatures. However, the seed 

 germinated also at low temperatures, almost down to zero, but very slowly. If spore germina- 

 tion and germination of the seed, is proportionately delayed here by lowering of the temperature, 

 it is not possible to understand how effectiveness can be obtained by cooling. Yet some effect 

 will appear if germination is increasingly delayed in older seed, but not to the same extent in 

 the smut spores. It is not advisable to use too low a temperature for experimental inoculation, 

 since development will only be prolonged ; on the contrary, it is questionable whether differences 

 of temperature in infected earth and in sprouting grain can favor infection. Further experi- 

 ments on this have just been made; they were very much impeded, however, in their exact carry- 

 ing out. 



The first experimental infections with the loose smut of oats on the blossoming grain could 

 be made only two years ago. Inoculation of the separate blossoms is possible in this case 

 only with very appreciable interference with and destruction of the blossoms. The time in which 

 the oat blossoms open can be determined only with difficulty and an artificial opening of the 

 blossoms necessitates a separation of the glumes, which are tightly closed. A high percent- 

 age of the harvested oat grain from a blossom inoculation was barren and a considerable 

 number failed in germination, probably as a result of the disturbance due to the mechanical 

 injury made during inoculation. The grains ultimately germinating were shown to have weak- 

 ened in germinating power and most of them withered subsequently. It must be added here 

 that wire worms appeared in the beds and destroyed all that were left, excepting a few plants 

 from which healthy plants were finally developed. 



Cylinder inoculation of the oat blossoms with the atomizer was then carried out. Most 

 of the blossoms of the oat panicles which hang downward were infected from below with smut 

 spores by this cylinder method of dissemination. The harvested seed, however, exclusive of 

 some isolated smutted plants, has resulted as yet only negatively. 



From the results obtained in inoculating the blossoms of oats with the loose smut, we can 

 indeed draw no final conclusion as yet, but can say this much : that blossom infection must be 

 only of lesser significance here ; and that, on the other hand, infection of the germinating seed- 

 lings in the soil, according to results already reported, is so much the more successful. There 

 are, however, a number of experiments where, according to our experience, the occurrence of 

 smutted plants scarcely makes possible any other explanation than that blossom infection must 

 also take place here. The circumstance that the blossoms of the oat panicle do not stand 

 upward, but hang downward, is not so favorable for direct inoculation of the blossoms in nature 

 by smut spores. The disseminated spores are not driven from below upward, but from above 

 downward. 



