43 



INFECTION OF THE MAIZE PLANT. 



It still remains necessary to subjoin the results of the investigations which were obtained 

 with maize smut and with the smut of Indian millet after the previous publication of Part 

 XI of this work. 



So far as the etiology of the smut is concerned, the annual repetitions of infection have 

 given only a confirmation of the earlier results, the fact that all sufficiently young plant parts 

 are susceptible to the germs of infection from without and that the smut itself is strictly local- 

 ized on the infected places, is confirmed even by the interesting small result that the stigmaS 

 of the pistillate blossom spikes, if inoculated when young enough with conidia of maize smut, 

 can subsequently produce smut phenomena. The stigma assumes a garland-like appearance, bends 

 over the swollen pouch-like places and ripens into a small spore mass which forms perfectly 

 ripe smut spores. Such a stigma bundle, deformed by the smut-pockets, forms a highly inter- 

 esting picture worth noticing, a reproduction of which is not necessary here, since it may easily 

 be imagined. Of course older parts of the stigma are no longer capable of inoculation. One 

 can at most observe the penetration of the germ-threads of the conidia. An effect of infection 

 leading after 2-3 weeks to ripe spore masses can no longer be observed here. The most dif- 

 ferent varieties of maize were grown for further experimental infections, especially the large 

 form of the horse-tooth maize. In this the infections were less easily successful because it was 

 harder to reach from the outside the sufficiently young tissue, which is tightly inclosed by leaves, 

 meeting together over the vegetative point, and because under the same condition the young 

 pistillate blossom spikes are more tightly closed from the outside by the overlapping of the envel- 

 oping leaves, than is the case in the smaller forms of maize. If the opening from above to the 

 pistillate spikes is widened and the fluid for infection with its conidia is introduced, no differ- 

 ences may be seen from the smaller varieties of maize. The same phenomena of smut already 

 described occur here also. Experiments were further carried out, to show that an infection of 

 the young germinating seedlings is one of the greatest rarities. All sufficiently young parts 

 of the matured plant are attacked if they are accessible from the outside for the germs of 

 infection. 



\Ve are concerned now only with showing how this infection takes place of itself in 

 nature. As already stated, it does not proceed directly from the smut spores. These smut 

 spores, which are not capable of germination in water, but may do so at any time in nutrient 

 solutions, produce conidial buds on saprophytic substrata, that is, in humus soil, and especially 

 in well manured earth. These conidia very soon pass over to the formation of air conidia 1 , 

 which are distributed through the air and are blown on to the maize plants, developing the 

 smut disease. 



(1) Compare with these the Illustrations of the yeast-like conidia and the air conidia, as well as 

 the forms of their gro\yth, on plate IV, Part V. 



