45 



Stone and Monahan, Day, 2 and Hunter 3 have made experi- 

 ments on the effect of forcing air through soil 

 in which plants were growing. The results are incon- 

 clusive and vary for different plants and for differ- 

 ent experiments. This is to he expected from a con- 

 sideraiton of the many ways in which such a pro- 

 cedure might alter the soil. Prohahly the disturbance 

 of water relations alone would account for the variabil- 

 ity of the results. The same uncertainty applies to 

 the experiments of Biesenbach 4 and Gausemann 5 who 

 planted trees in holes partly filled wit& brushwood 

 and other loose material, which was supposed to facili- 

 tate aeration. Ho doubt aeration was facilitated but 

 it is probable that change -©# water relations and the 

 supply of organic matter were more important. It has 



1. Mass. Agr. Exp. Sta. , Report 1905 : 115-145. 



2. Ontario Agr. Coll. and Exp. Farm, Report 

 31: 37-40 (1905), 32: 30-37 (1906). 



3. Proc. Univ. Durham Phil. Soc. 4: 183-186 

 (I9il-1912). For incidental experiments of Cannon see 

 Cannon and Free,- Science 45: 178 (1917). The similar 

 experiments of Uoyes and others with carbon dioxide will 

 be discussed below (page* ?X~ )• 



4. Deut. landw. Presse 30: 752 (1903). 



5. Deut. landw. Presse 31: 619-620 (1904). 



