49 



Varieties of millet with black grains and with white ones were used. The result, which con- 

 tinued to be the same in succeeding years, was the most favorable conceivable, namely, a total 

 infection of all the plants under experimentation. The variety of millet with white grains is best 

 suited to give striking and beautiful illustrations of smut phenomena. The plants obtained a 

 height of more than 4 feet and the galls of smutted ones became a large as a walnut. 



An experimental object more favorable for the inoculation of young seed than that exist- 

 ing hero in millet is scarcely conceivable. It is still undecided, however, whether infection takes 

 place only on the young germinating seedling or whether it can also take place successfully 

 in the blossoms. The proof of air conidia in this form favors the infection of the blossoms 

 of the host plant. The single blossoms of these host plants are, however, so small that the prob- 

 ability of blossom infection is thereby greatly reduced. It should be added to this that the smut 

 galls in experimental fields are not disseminated and therefore could not succeed in reaching 

 the soil directly, so that any direct formation of air conidia is thereby practically prevented. 

 Infection must then have taken place from the conidia of a saprophytic nutrition. They can 

 be formed on the upper surface of the soil from spores which had been previously dissem- 

 inated. The probability that this may happen is not great. Still greater, however, is the 

 other probability that in sowing millet in the open air the young germinating seedlings are 

 reached by air conidia. Practical experiments on the inoculation of the blossoms resulted nega- 

 tively. Infection of the blossoms is, however, in no way excluded by this, but is reduced to a 

 minimum. 



Experiments with Setaria Italica with its smut forms had about the same results as those 

 described above for Panicum. A black shimmer may be seen in this thick, club-like inflores- 

 cence, already infected, when the ripe ovules rupture, freeing the smut. The black smut spores 

 are not disseminated. They usually remain so enclosed in the thick panicle of Italian millet 

 that close examination is necessary in order to recognize plants attacked by smut. It often 

 occurs here that only a part of the blossoms of a panicle are attacked and that normal blossoms 

 free from smut may be found between the diseased ones. The smut spores in any case germi- 

 nate into four-celled hemibasidia, in which often no conidia at all occur, which, if they do 

 appear, however, grow out very quickly into germinating tubes. Air conidia have not been 

 observed in cultures of these spores. Smut spores, obtained pure in the autumn, germinated in 

 the spring, easily and surely, especially in dilute nutrient solutions. They were used further 

 only after purification with a centrifugal sieve and after one day's retention in dilute nutrient 

 solution. They were sprayed on the seedlings of Setaria which had been thus prepared and 

 were just germinating. The cultures were treated as above and the infected seedlings, when 

 they had reached a sufficient size, were planted out of doors. These seedlings are exceedingly 

 small, so that one might suppose inoculation by spraying with spores would have no result in 

 the experimental plants. Experience, however, proves the opposite ; as high as 70% of smutted 

 plants were obtained and it was possible to achieve here, as in Indian millet, and Panicum, a total 

 infection, by using for this infection seed which is somewhat older and therefore sprouts more 

 slowly. 



