June 15, 1920 Relation of Rust in Seed Wheat to Seedling Infection 269 



grain elevator in Minneapolis, Minn. ; one lot of durum from Hagen, N. 

 Dak.; and one mixed lot from Fargo, N. Dak. From all of these wheats 

 rusted seed was selected and sown on November 8, 191 5, in the isolated 

 room. Seven hundred and six plants were obtained from this seed and 

 grown to maturity. No rust appeared upon any of the plants at any 

 time. On the primary leaf of two different plants lesions appeared from 

 which cultures of Helminthosporium sp. were obtained. No other infec- 

 tion of any kind appeared upon any of these plants. Plate 41, B, shows 

 three flats of plants from this experiment just after the plants were well 

 headed. 



Experiment 2. — Experiment i was carried on during the winter months, 

 and it was thought advisable, therefore, to duplicate the work in the 

 spring and sow the seed at the time spring wheat normally would be 

 sown in the field. The same precautions were taken as in experiment i, 

 and the same room was used. Seed was secured from the following 

 sources: Three lots of mixed seed of unknown source from Minneapolis, 

 Minn. ; two lots of mixed seed of unknown origin from Minneapolis, 

 Minn.; three lots of durum from the rust nursery, University Farm, 

 St. Paul, Minn.; one lot of durum from Clark, S. Dak.; two lots of 

 durum from the cereal -disease plots at Madison, Wis.; one lot of Mar- 

 quis from Maynard, Iowa; one lot of durum from Leith, S. Dak.; one 

 lot of mixed seed from Armour, S. Dak. Rusted kernels from these 

 sources were sown on March 19, 1916, and 730 plants emerged and were 

 grown to maturity. No rust appeared on any of these plants at any 

 time. The experiment was discontinued when the wheat became mature. 



Experiment 3. — The experiment was repeated during the winter of 

 1 91 6-1 7, when 760 plants were grown to maturity under the same con- 

 ditions as outlined above. Seed for this experiment was obtained from 

 various places in North and South Dakota and Minnesota. No rust 

 appeared upon these plants at any time. The experiment was concluded 

 when the plants were mature. 



Experiment 4. — It was thought possible that soil temperatures at 

 the time of the germination of the seed might affect the ability of the 

 fungus to penetrate the young embryo and that the temperature in the 

 isolated room might have been too high for successful infection at the 

 time of germination. In order to simulate more closely natural condi- 

 tions of germination and growth of the plants, infected wheat kernels 

 were germinated in soil in an Altmann incubator at different temperatures 

 as indicated in Table III. 



When the seedlings were about iK inches long, they were carefully 

 transferred to pots of sterilized soil and grown in the isolated room until 

 the plants were mature. Twenty-five kernels of wheat were used for 

 each temperature indicated. No rust appeared upon these plants at 

 any time. 



