448 THE CANADIAN NATURALIST. [Vol. X. 



3rd. — The plant No. II., wliich was placed in the most favor- 

 able position as regards sunshine and rain, absorbed a greater 

 amount of soluble iron and soluble phosphoric acid than plant 

 No. III., which was grown in a less favorable position. Whether 

 the plants have the power of selecting and taking up by their 

 rootlets these compounds from the manured soil, or whether the 

 plants simply absorb any substance in solution supplied to them, 

 I am unable to say; but it appears that the healthy condition 

 and gigantic growth of the plants Nos. II. and III. were 

 due to the fact that they were supplied with iron (in a soluble 

 form, FeS04) '^'^^ phosphoric acid also in a soluble form. 



I am inclined to think that a fairly large proportion of soluble 

 iron and soluble phosphates in a soil is favorable to the growth 

 of plants of a deep green color (that is, plants which develop 

 a large amount of chlorophyll cells), like the varieties of cab- 

 bage. 



From the researches conducted by Mr. F. C. Phillips, of the 

 United States, " On the Absorption of Metallic Oxides by 

 Plants" (Chemical News, vol. xlvi., 224), it seems that his 

 experiments confirm the nondiscriminating theory of plant 

 absorption of Dr. Freytag. 



Pnblished March 8, 1888. 



