17 



It must then be asked which of the two is the more effective in any especial case. Besides this a 

 third case is possible,— that only one of the two infection forms exists alone, either the infection 

 of the germinating seedlings or that of the blossoms. The experimental infection undertaken 

 on young germinating seedlings for supplementation and comparison cannot be made in the same 

 season, in summer, as are blossom infections, and for these the same favorable circumstance 

 does not hold good any longer, that is, the capacity for germination of fresh smut material. It 

 is necessary to make these experiments in spring with smut spores harvested from the field during 

 the previous summer and further with grain taken from the same fields, which are, however, 

 free from smut. 



The gathering of spore material, which must remain fresh and uninjured until the next 

 spring, is no easy matter. The spore masses are unavoidably polluted by the air even up to the 

 time of ripening, they are detrimentally influenced by occasional rain and especially by insects 

 which creep into the spore masses, eat the spores and when possible deposit their eggs there. 

 Smut material gathered, without special precaution, from the attacked inflorescences of grain 

 will certainly be damaged in the following spring by worms, often indeed being made useless. 

 Very special precautionary measures and peculiar methods are needed in order to get sufficient 

 amounts of pure smut material in summer with the assurance that it has been protected from 

 all injurious influences. From a long series of experiments, the following method has been proved 

 best for obtaining pure smut material for infection the following spring. Spore material is 

 gathered in sufficient amounts, soon after the breaking open of the spore masses, before any 

 injurious influences have made themselves felt, and is kept eight days in a dry place. Then the 

 smut spores are carefully sifted on to white paper through a fine copper sieve which lets through 

 only the spores. The refuse remaining on the sieve is thrown away. Experience has proved 

 that the smut material thus sieved can be as well kept as possible in this powdery form until 

 the next spring and particularly that no insects will enter the smut spores. These sieved spores 

 are carefully put in a number of small flasks with flat bases, which are filled not more than one- 

 fourth to one-fifth. The wide neck is closed carefully with sterilized paper and the spores are kept 

 in a cool, dry place through the winter. The preservation of spores in many small flasks has the 

 especial advantage that if any injurious influence is present in one small flask, the other spores 

 were protected from it. In fact, in this form, the material to be used for infecting germinat- 

 ing seedlings has shown in every case that it has been well protected so that it can be used in the 

 freshest possible condition. In spring, shortly before using, the spores are put in clean water and 

 thrown about five or six times on a centrifugal sieve. The spores thrown out quickly have been 

 proved to be almost perfectly pure and cultures may be made with these spores in a nutrient solu- 

 tion which show scarcely any pollution throughout the period of culture. The treatment of spores 

 in this form has the additional advantage that, by the day's retention in water necessary for the 

 purification of the spores, they are prepared as favorably as possible for germination, and that 

 spores, which are then sprayed in a dilute nutrient solution on the germinating seedling already 

 prepared, will germinate without loss of time in the drops sprayed on the seedling and can pene- 

 trate into it directly. For this infection of germinating seedlings, it is not advantageous to 

 use conidia which appear in spore germination and increase almost indefinitely by budding 



