39 



Alway 1 cereal roots may reach 7 feet in Saskatchewan* 

 Pfeffer records roots of clover and of Lathy rus sylvestris 

 at 2 to 3 meters. 2 Again, the roots which are able to 

 penetrate deeply into water-saturated soils certainly 

 cannot receive important supplies of atmospheric oxygen, 

 regardless of the actual depths at which they lie* 



Direct evidence as to root respiration and aera- 

 tion might be obtained, perhaps, from a systematic study 

 of the composition of the gases present in the root pas- 

 sages. However, the information now available is not 

 sufficient for any conclusions. The internal air of 

 several roots has been analyzed by Dutrochet, Heintz7 

 and Devaux. All found the carbon dioxide content higher 

 and the oxygen content lower than in the open atmosphere 

 or in the ordinary soil air. As might be expected there 

 is great individual variation. The same enrichment in 



1. Quoted by Hilgard,-, Soils, p. 171 (1906). 



2. Physiol, of Plants, vol. 1, p. 153 (1900). 



3. Memoires, etc., p. 175 (1837). 



4. Ber. chem. Ges. 6: 670 (1873). 



5. Ann. sci. nat. (7) 14: 352 (1891); Rev. 

 gen. bot. 3: 49 (1891). 



