SELENIUM ABSORPTION BY PLANTS AND 

 THEIR RESULTING TOXICITY TO ANIMALS 



By Annie M. HuKD-KAEBEat 



Associate Plant Physiologist, Bureau of Plant Industry, United States Depart- 

 ment of Agriculture 



(With 6 plates) 



Unknown before 1817, selenium has been of interest primarily to 

 physicists and inventors since 1873, when its remarkable photoelec- 

 tric properties were discovered. Now it becomes of importance to 

 the biologist and to the farmer as the cause of a serious disease of 

 livestock known locally as " alkali disease 'V although it may more 

 properly be referred to as the selenium disease (Knight, 1935). 

 About 20 years ago the plant physiologist added selenium to the list 

 of elements known to be taken up from the earth by plants (Gass- 

 mann, 1917, 1919) ; and now the farmer of certain sections is 

 faced with the fact that its presence in his land renders his crops 

 unfit for food. 



The selenium disease appears to be unique in that as far as is now 

 known it is the only disease caused by vegetation made poisonous by 

 an element absorbed from a virgin soil. It is fortunate that such 

 soils are not more widely distributed. 



Selenium occurs in many parts of the world combined with the 

 heavy metals such as lead, silver, and copper, and in pyrites (Strock, 

 1935; Williams and Byers, 1934). It is commonly associated with 

 sulphur of volcanic origin and is found in meteoric iron. Of the 

 approximately 90 known elements it is about fiftieth in order of 

 abundance, being just about as rare as silver (Noddack and Noddack, 

 1934). Traces of it are found in soils derived from shales over 

 much of the United States (Byers, 1935) ; but only in certain re- 

 stricted areas of the Middle West is it known to malve vegetation 

 toxic (Franke et al., 1934). 



In France it has been found in the vegetation along canals from 

 mineral springs containing selenium (Taboury, 1932) . In Germany 



^ This name is a misnomer, the trouble being entirely different from that caused by an 

 excess of certain salts in the water. 



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