EESULTS WITH PURE SOLUTIONS. 



13 



the limits for the Dagdi Juar variety are given; in that of Avena 

 satiuo, those for the Red Algerian variety of oats: in that of Gos- 

 sypium harbadense, those for the Jannovitch Egyptian variety of 

 cotton, and in that of Beta vulgaris, those for the Original Kleinwanz- 

 leben strain of sugar beets. 



A glance at Table VI shows that not only do the different species 

 differ vastly in the absolute degree of their resistance to the toxic 

 action of these pure solutions, but the order of toxicity of the several 

 salts varies considerably with respect to different species. For con- 

 venience of comparison, the order of toxicity of the six salts to each 

 of the eight species is stated in Table VII. 



Table YII. — Order of toxicity of the different salts to each plant. 



Lupinus 



Medicago 



Triticum 



Zea mays. 



Andropo- 



Avena 



Gossypium 



Beta 



albu . 



sativa. 



vulgare. 



ghum. 



sativa. 



barbadense. 



vulgaris. 



MgS0 4 



MgS0 4 



MgS0 4 * 



Na»C0 3 



MgCl.-. 



MgS0 4 * 



MgS0 4 



MgS0 4 * 



MgClo 



MgClo 



MgCl. * 



NaCl 



MgSo 4 



MgClo* 



MgClo 



MgCl,* 



Na C0 3 



NaoC0 3 



Na COj 



NaHCO,* 



NaoC0 3 



Na.,C0 3 



Na.XO^* 



Xa. CO, 



XaHCOj 



Na 2 S0 4 



NaHC0 3 



Xa.,S0 4 * 

 MgCla 



NaHC0 3 



XaHCOj 



Xa,$0.* 



NaHC0 3 



Xa,?0 4 



XaCl 



Na«S0 4 



NaoS0 4 



Na-,S01 4 



NaClf 



Na SO, 



XaCl 



NaHCO d 



NaCl 



MgS0 4 



NaCl 



NaCl 



NaHCOgf 



XaCl 



Equally toxic. 



Equally toxic. 



A study of Table VII shows that, with the single exception of maize, 

 the salts of magnesium are more toxic than those of sodium to all the 

 plants tested. a This exception is the more remarkable since three other 

 plants of the same family — wheat, oats, and sorghum — are included in the 

 experiments. In most cases the sulphate of magnesium is more toxic 

 than the chlorid. Sodium carbonate is from twice to four times as toxic 

 to the white lupine, wheat, and maize as is the acid carbonate (bicarbon- 

 ate), while to the other plants it is only slightly more toxic than the 

 latter. Sodium sulphate, which is generally regarded as a less inju- 

 rious component of "alkali" soils than sodium chlorid, in pure solu- 

 tions is more toxic to nearly all the plants tested. 



Returning to Table VI in order to compare the powers of resist- 

 ance of the different plants, we find that maize is on the whole decid- 

 edly the most and cotton the least resistant of them all. Wheat 

 stands next to maize among the more tolerant species, while the beet 

 is on the whole the least resistant after cotton. How difficult it is 

 to explain the behavior of plants in relation to saline soils as they 

 occur in nature on the basis of such results as these with solutions of 

 single salts, is shown by the fact that while the sugar beet is one of the 

 plants best adapted to soils of that character, maize is generally 

 regarded as very sensitive. 



°To the Early Amber variety of sorghum, however, sodium carbonate is nearly 

 or quite as toxic as the magnesium salts. 



113 



