312 AMERICAN JOURNAL OF BOTANY , [Vol. 9, 



with nutrient solutions. His analyses of the tops show that when trans- 

 piration was increased sometimes the amount of ash increased and some- 

 times it decreased. Ilienkoff (1865) found no correlation between the 

 quantity bi water' supplied and the total a^h conlrerit of buckwheat plants 

 the tops of which were analyzed after growing f6r k period of 67 days. 

 Fittbogen (1873) found no significant difference in the quantity of ash 

 found for a unit of water transpired by oat plants growing in soil in which 

 the water varied froih 20 to 6d perceirit of its water-holding capacity. 



Thorn and Holtz (1917) presented data that show that in general as the 

 concentration of the soil solution is increased the water requirement of 

 wheat and barley plants decreases as does ,also the quantity of water, trans- 

 pired pergrani of ash found in the plant. Their table at the top of page 

 50 shows that the ash content in the whole plants, expressed in percentage 

 of dry weight, is about the same regardless of the concentratiori of the nutri- 

 ent solution in which they were grown, excepting in a very high concentra- 

 tion which was injurious to growth. ,, 



The effect of decreased transpiration brought about by shadjng has 

 been worked on first by Schloessing (1869), and more recently by Hassel- 

 bring (1914 a, b). Schloessing found that a tobacco plant under a shaded 

 bell jar which transpired the least also possessed the smaller dry weight and 

 ash content. Hasselbring, also working with tobacco plants, found, on 

 the other hand, a smaller absolute amount and percentage of ash in the 

 plants which transpired the most. The dry weight was practically tjie 

 same in plants grown in the open sunlight and in the shade. He stated 

 that it appears, therefore, that the absorption of salts by roots is independ- 

 ent of the absorption of water, and that the transpiration stream does riot 

 exert an accelerating effect on the entrance of salts. 



Sorauer (1880) and Wollney (1898 a, .b) worked on the relation of ab- 

 sorption of salts and transpiration as affected by atmospheric humidity. 

 Sorauer found that pea plants growing in a dry chamber had a slightly 

 greater dry weight and ash content than similar plants growing in humid 

 chambers. Wollney, working with several crop plants grown in chambers 

 with high, medium, and low humidity, found that in general the absolute 

 green weight and dry matter was somewhat greater in the plants grown 

 in the more humid atmosphere. The percentage of ash and dry matter in 

 general increased slightly with the dryness of the air. Kiesselbach (1916) 

 found no, distinct correlation between transpiration and the absofute quan- 

 tity or percentage of ash or between the water requirement and ash found 

 in corn plants grown in dry and humid greenhouses, or in different degrees 

 of soil-moisture content. Curtis (1920) mentioned some unpublished data 

 showing that doubling the transpiration of barley plants growing with their 

 roots in rititrierit Solution has no' tfeiideridy to increase sdlt absorptiori when 

 the transpiration is incrfealsed by decreiasing the atmospheric humidity. 



Several authors have compared the absorption of mineral' nutri'eilts 'and 



