SELENIUM — HURD-KARRER 



299 



sorption of the cereals is associated with a lower selenium intake. 

 The Leguminoseae (legume family) have in general been inter- 

 mediate (table 2). 



Obviously, then, the safest crops to grow on seleniferous soils are 

 cereals and grasses; and these are the crops that are chiefly raised 

 on them now. Since all plants require sulphur, there is little likeli- 

 hood of any plant being entirely unable to take up selenium. 



That certain plants accumulate more selenium than others was 

 first observed by Byers, who found that a certain wild aster {Aster 

 muUiflorus) growing in the seleniferous-soil areas (South Dakota) 

 always contained more selenium than did the other vegetation. 

 Shortly thereafter Beath and his coworkers (1934) fomid that cer- 

 tain plants in a different area (Wyoming) also absorbed it at an 

 extraordinary rate. One species of Astragalus was found to take 

 up as much as a tenth of 1 percent of the air-dry weight of the 

 tissues, apparently without injury (Beath, Draize, Eppson, et al., 

 1934a). Byers (1935) subsequently showed that ^4sifr«^aZws 625wZc«;^w5 

 consistently absorbed several hundred times as much selenium as 

 another species of the same genus {A. missouriensis) growing beside 

 it. He found the enormously high selenium concentration of 9,120 

 parts per million in Oonopsis condensata. 



Table 5. — Comparative absorption of selenium and sulphur by some crop plants 

 grown in greenhouse plots to tuhich 5 parts per million selenium {as sodium 

 selenate) was added to the soil. (Figures are parts per million based on 

 air-dry Height of tissues)^ 



Plant 



Broccoli. 



Oats 



Barley... 

 Wheat... 

 Spinach. 



Selenium 

 in plants 



1,330 

 740 

 640 

 550 

 430 



Sulphur 

 in plants 



32, 300 

 14, 800 

 13, 600 

 12, 200 

 9,000 



'Analyses made under the direction of Dr. E. C. Shorey, U. S. Bureau of Plant Industry. 



Although selenium-containing grain seems to be normal, animals 

 to which it is fed are able to detect something in it they do not like. 

 The rats of the grain-feeding experiments (Hurd-Karrer and 

 Kennedy) invariably refused to eat much for about a week, although 

 later they ate normal amounts. However, others persisted indefi- 

 nitely in their refusal to eat. Thus some young spinach grown in 

 selenized soil in the greenhouse and containing between 300 and 400 

 parts per million selenium remained almost untouched, the rats pre- 

 ferring to starve for the 3-day intervals during which it was left 

 in their cages. This spinach was fresh and succulent and with every 

 outward appearance of being desirable food. But the rats detected 

 the presence of the selenium, for when market spinach was sub- 



