Sept. 1907] Cultures of Uredineae in i?o6 *J X 201 



The following three species have never before been tested 

 by means of cultures, so far as the writer knows. Although few 

 in number, they make an important addition to our knowledge of 

 life histories: 



i. Melampsora Lini (Link) Desmaz. For a number of 

 years attempts have been made to obtain cultures of this cosmo- 

 politan rust, and learn its full cycle of development. Many col- 

 lections from different parts of the country, gathered at different 

 times from November to April, have been tested, but with uni- 

 form failure to secure germination of the teliospores. The most 

 numerous and promising collections were sent by Professor H. 

 L. Bolley, of North Dakota, but equally in vain until one made 

 the last day of April on cultivated flax, dug from under a snow 

 bank, was received. This showed strong germination of the 

 teliospores, and on May 4 was sown on Linum Lewisii, Larix 

 laricina, and the day following on Tsuga canadensis, and Ari- 

 saema triphyllum. No clues were available, but judging from 

 the willow, poplar, and some other species of the same genus, it 

 was assumed that it might be heteroecious. Nevertheless, on 

 May 16 pycnia began to appear on the flax, and on May 21 aecia. 

 The next sowing was made May 18 on Linum usitatissimum, 

 plants of which had not before been available, giving rise to 

 pycnia May 26, and aecia May 30. Another equally successful 

 sowing on the same host was made May 29, but exact record 

 for the appearance of the sori was not kept. 



The pycnia are small, pale, and inconspicuous, although 

 numerous. They are globoid, subepidermal, and without ostiolar 

 filaments. The aecia are of the caeoma form, that is, are with- 

 out peridia. They are also rather pale, and not as prominent 

 as the uredinia, for which, however, they might easily be mis- 

 taken. So far as I can learn they have never been collected, 

 although probably common throughout the world. This may 

 be due to their being inconspicuous, and quite as much to the 

 earliness of their appearance. 



The economic bearing of the discovery is to some extent 

 obvious. Knowing the autoecious nature of the rust makes the 

 destruction of old flax straw in flax growing regions a matter 

 of moment, in order to lessen and retard the appearance of the 

 rust in growing fields of flax. Upon reporting the first success 

 to Professor Bolley he replied under date of May 23, 1906: "I 

 am very much pleased to receive your letter, for with the in- 

 formation I am able to determine the source of a rust epidemic 

 that we had in our flax breeding plots last year. I now find 

 everywhere in the flax stubble plenty of volunteer flax with 

 almost every plant more or less infected with spermogonia and 

 aecidia." It will now be possible to intelligently devise methods 

 for the practical control of flax rust. 



