10 WHEAT RESISTANCE TO TOXIC SALTS. 



tive resistance of tliit'ereiit varieties, or races, of a single species has 

 received little attention.'^ 



During the autumn of lOO)), and again in 1004, the writer had occa- 

 sion to re})eat. at tlie Departiucnt of Agriculture. AVashington, I). C. 

 the experiments previously conducted b}^ Kearne}^ and Cameron wiOi 



nnii. lie foiuid tlie limit of /'ixiiiii .■^ulinnii to be -^jIq-q gram mol. per liter for 

 copper suli»li!ite (CuSOJ as the strengtli wbit-h will barely ]H'riuit the roots to 

 Hve, and that for Zca viuiix to be osooo- I^*^' ohtained results with various 

 salts, but this will sulHce to show the variability between plnuts widely sep- 

 arated in relationshi]). 



Moore and Kellermun (A ]\Iethod of Destroying or Preventing the Growth of 

 Algte and Certain Pathogenic P>acteria in "Water Sup])lies, lUil. VA. P>ureau of 

 Plant Industry, U. S. Department of Agriculture, T.Xi-t) say: 



In dealing with alga- the toxic concentration varies greatly for different gen- 

 era, even for different species of the same genus. Niigeli demonstrated the 

 extreme sensitiveness of iiplroiiijia iiitida and >S. dubiu to the presence of copper 

 coins ill the water. Oscillatorhi. Chidopliora, (Edogoiinun, and the diatoms 

 succumb in six hours to a copper-sulphate solution of 1 to 20,000 and in two 

 days to 1 to 50,000 according to I'okorny. * * ■■' According to Ono, weak 

 solutions of the salts of most of the metals encourage the growth of alga^ and 

 fungi. Mercury and copper, however, at O.OOdO.") jier cent and O.OOCOl jier cent, 

 respectively, distinctly inhibit growth. This was the <-ase with !<li<ir(jcl(iniiiiii, 

 Chroococciis, and Protorovvn^. 



Moore and Kellerman have obtained results with a.lga' which serve very well 

 to illustrate the variability of these organisms in the presence of the toxic cop- 

 per sulphate. They found that with tliis salt 1 to 25,000, 1 to 75,000, and 1 to 

 100,000 were sutHcient to kill RapJiiditim pulj/iiioi-pliKiii in four days. DesjuidinDi 

 {iirartzii in three days, and Xaricnla sp. in live days, respectively. One part 

 of salt to .'500,000 of water and 1 to l.OOO.OOO were f.atal to Coiifcrni hoiiihi/ciiium 

 in three days and »V//;/»r(/ itvcUa in a few minutes. Clostcriinn iiioiiilifo-iini was 

 killed in four days in a 1 to .500,000 solution, and Aiiulxniu /loK-atjiiir in a 1 to 

 0,000,000 solution in seventy-two hours. The most sensitive of all was i ioi/Iciki 

 (unericaiia, practically all of which were killed in a 1 to 10,000,000 solution in 

 sixteen hours. 



o J. F. Breazeale informs the writer that in water-cultui'e ex])erinients in 

 the laboratory of the I>ure;ui of Soils. United States Department of Agriculture, 

 he has found a very wide variation in the development of seedlings of different 

 varieties of wheat when grown in the same artificial nutrient solutions and also 

 aqueous extracts of soil, and W. II. Ileileman. in the same laboratory, has shown 

 very similar results to those i)resented in this investigation when using different 

 varieties of wheat in i)ot cultures of natural and artificial alkali soils. It has 

 also been shown that the vig(n' and rate of gernunation of seeds of different 

 varieties are very different when previously soaked in any given solution of an 

 electrolyte. 



Cameron and Breazeale (The Toxic Action of Acids and Salts on Seedlings, 

 Journal Phys. Chem.. vol. S. No. 1, p. 1, Jan., 1904) have shown ;i wide varia- 

 tion in the toxic action of different salts and acids on seedlings of plants widely 

 separated in relationship. 



From certain ])oints of view, especially as bearing on current chemical theo- 

 ries, the paper of Dandeno (American Journal of Science, Vol. XVII, June, 

 1904) in this field is especially interesting, but a direct comparison of results 

 in toxic salt solutions can not be made, owing to the fact that seedlings of differ- 

 ent plants have been used. 



