222 GRASSES OF IOWA. 



shown that Kuehn was in error, at least for some of our smuts. 

 Because, however, of Kuehn 's work, it was recommended to 

 treat seed corn as v. heat seed was treated for bunt. In 1692 

 experiments were made at the Iowa Agricultural College* with 

 corn, in which seed was treated with hot water heated up to 53 

 -Do'^ C. ; also ammoniacal carbonate of copper, and copper sul- 

 phate. The hot water treatment, as the work of Stewart indi- 

 cated, could not have been effectual, since the smut spores can 

 be heated higher than corn. The other treatment should have 

 been effectual, since the smut spores are sensitive to copper 

 solutions. In all cases there was no appreciable difference 

 between treated and check. Independently of this work, the 

 botanists of the Kansas Experiment Stitionf made some exper- 

 iments from which the following conclusions were drawn: 



"Further investigation is necessary in order to determine the 

 mode of infection — a point that must be settled before we can 

 hope to employ rational methods for the prevention of this 

 annoying -and destructive pest. " 



More complete experiments made by Hitchcock and Norton J 

 indicate that: 



1. " Infection may take place at anytime of the season 

 when the corn is growing, and does not depend so much on the 

 time of the season as on the stage of develop aaent of the plant. 



2. "Infection may take place in any part of the plant 

 where growing tissue is present, and at any time in its life, 

 but scarcely ever before the plant has attained the height of 

 three feet. 



3. "After the tissues are hardened, the smut cannot pene- 

 trate them, and consequently infection do3S not take place in 

 older parts of the corn, but only in the growing tissues. This 

 growing condition is found in the young leaves when the first 

 smut appears in the field; later it occurs mostly at the junction 

 of the leaf and sheath, where cells are present for a long time 

 in a stite of growth, and are consequently exposed longer to 

 penetration by the germ tubes from the conidia; still later this 

 is found in the flowers and young parts of the ear and tassel; 

 while finally the only parts open to infection are the rudimen- 

 tary ears, which develop after the larger ears, at each joint on 

 the lower part of the stalk. 



*Ball. Iowa Agrl. Exp. Sta. 25. 315. See also Bull. 20. 721. 

 tBull. Kansas Agrl. Exp. Sta. 23: 315. 

 *Bull. Kansas Agrl. Exp. Sta. 62: 183-187. 



