CEREAL PESTS PARASITIC FUNGI 527 



conditions. It was shown that infection by these smuts 

 takes place during the period of blossoming, the spores 

 falling directly upon the stigmas, there germinating. 

 Instead of producing primary and secondary conidia, 

 these germinating spores directly infect the young ovary, 

 but do not seem to interfere seriously with the comple- 

 tion of its development. The smut resulting from this 

 infection, therefore, appears in the next year's crop. 

 However, if the seed is microscopically examined latent 

 hyphse of the parasites will be seen. After planting the 

 seed in the spring, these latent hyphse resume their growth 

 and infect the growing point of the young plant. Later 

 the spores from the resulting diseased spikes are distrib- 

 uted just in time to fall on healthy wheat spikes when 

 they are in blossom and again cause infection of the seed 

 of the next crop. Stools of wheat infected with loose 

 smut may be readily detected, as they are usually shorter 

 than the healthy stools and have a purplish color (Fig. 164). 



569. Naked smut of barley ( Ustilago nuda, Kell. & 

 Sw.). As in the case of loose smut of wheat, this smut 

 develops rapidly within the tissues of the host, and ma- 

 tures its spores at a time sufficiently early to insure infec- 

 tion of the blossoms of healthy plants. The spores lodg- 

 ing directly upon the stigma, germinate in a manner 

 simulating that of the pollen grain, the germ tube enter- 

 ing the ovary directly without the previous development 

 of conidia. As in the loose smut of wheat, the invading 

 mycelium lies dormant in the tissues of the seed, but 

 renews its growth the next spring after germination of the 

 latter, and matures in that year's crop (Fig. 165). 



570. Control measures. Various methods of treat- 

 ment for these last-described smuts of wheat and barley 

 have been tried, usually without success. Chemical 



