306 STATE BOARD OF AGRICULTURE. 



cased plants is often retained iu greater part witliin tlie uppermost 

 slioatli. Before the spores are ripe tlie culm is somewhat swollen and 

 more or less twisted and misshapen, showing black streaks whidi are 

 the regions where the spores are present in great abundance. These 

 streaks may be present even in the sheatli or in tlie leaves. On cross 

 section black areas appear corresponding to these streaks. The liead 

 either rcnuiins unchanged, except that it dries up, or may show distor- 

 tion of the lower spikelets, these being filled with the black masses of 

 the spores. As the spores ripen the swollen parts shrink and split open 

 over the elongated spore masses, alloAving the spores to escape as a black 

 powder. This takes place just about the time for harvesting the grain. 

 The diseased plants stool but little and are usuallv only two-thirds to 

 three-fourths as tall as the healthy plants. 



Three tyjies of smut infection are now recognized by plant patholog- 

 ists : (1) at all actively growing parts of the plant for a considerable 

 ])eriod of the growth of the plant, as in corn smut; (2) at the blossom- 

 ing i)eriod of the plant, the fungus growing into the developing seed 

 within the flower without destroying it and keeping pace with the 

 growth of the plant that grows from the seed, not becoming visible ex- 

 ternally until shortly before the time of flowering when the flowers and 

 often all the adjacent parts are found to be filled with the spores of the 

 smut, to the total destruction of these i)arts, as in the loose smut of 

 wheat and barley; (3) just as the seedling is emerging from the seed, in- 

 fection occurring from spores of the smut that have renuiined attached 

 to the seed when it was planted or that were in the soil, as in oat smut 

 or bunt of wheat. 



The location of the smut infection throughout the rye plant instead 

 of merely at the growing regions, indicates- that the rye smut does not 

 have the first type of infection. In the summer of 1915 Dr. G. H. Coons 

 attempted blossom infections by dusting fresh spores of this smut upon 

 the heads of rye as they were in blossom and by rubbing the spores into 

 the spikelets, planting the seeds obtained from these heads in the Botan- 

 ical Garden. In June, 191G, these plants were absolutely free from the 

 smut, showing tliat no blossom infection had taken place. This was to 

 be expected from the fact that the spores are not shed at the blossoming 

 period of the rye but at harvest time. In the meantime a bulletin was 

 issued by the Minnesota Experiment Station* stating that the infection 

 was of the third type, i. e., seedling infection. This bulletin was not yet 

 at hand when the following experiment was begun to determine this 

 point. On September 23, 191G, seeds of Rosen rye obtained from the 

 Department of Farm Crojis of this institution were treated with spores 

 of the rye smut freshly scraped from diseased culms collected by the 

 senior author in July and August. The treated grain was planted in 

 the Botanical Garden in rows about seven feet long and a foot apart. 

 About 100 plants came up in each row. The treatments of the seeds were 

 as follows: 



Row 1 — No smut spores, no disinfecting treatment; control row. 



Row 2 — Dry seed rolled in dry spores, no disinfecting treatment. 



Row 3 — Wet seed rolled in dry spores, no disinfecting treatment. 



Row 4 — Like row 1; control. 



♦Stakman, E. C. and Levine, M. N. Rye Smut. The University of Minn. Agri. Exp. Sta. 

 Bui. 160, 19 pages, 6 figures. Aug., 1916. 



