84 



soil . Mitscherlicli ., however, secured no increase of 

 yield by irrigation with water saturated with carbon 

 dioxide. It is possible, as suggested by Hansen 3 , that 

 the benefit derived from forcing carbon dioxide through 

 the soil is really due to a slight enrichment of the 

 air immediately above by means of the escaping gas, this 

 enrichment being beneficial to the aerial parts of the 

 plants. The experiments of Gannon, later described in 

 detail 4 , and one experiment included in the present 

 investigation^ indicate specific effects of carbon dioxide 

 on roots" but the tests are not numerous enough to per- 

 mit clear dissociation from the effects of the mere 



1. Demoussy,- C. R. 138; 2yl-2y3 (1904); 

 V/agner,- I'itth. deut. landw. Ges. 25: 176-179 (1910); 

 Hansen,- iJaturw. Rundschau 27: 547-550 (1912); Hiltner,- 

 Prakt. Bl. Pflanzenbau and Schutz (n.s. ) 11: 45-52 (1913); 

 Bornemann,- Llitth. deut. landw. Ges. 8: 443-445 (1913); 

 Quarrie,- Commercial Pert. 8: 26c (1914); Reinau and 

 Xlain,- Gartenwelt 18: 214-218 (1914). 



2. Landw. Jahrb. 39: 15 7-166 (1910). 



3. Ilaturw. Rundschau 27i 547-550 ( 1918 ) . 



4. See pages ?•£—' 



5. Page /«L/ • 



6. See especially Gar. Inst, of V/ash. , Year- " 

 book 15: 74-75 (1916) and Gannon and Pree,- Science 45: 

 178 (lyi7j. 



