340 Physiologie. 



0,008 gm. of iron per liter than with 0,002 gm. When judged by 

 the growth of plants ferrous sulphate, ferric citrate, and ferric tar- 

 trate afforded sufficient iron when used in proper quantities in the 

 acid and neutral Solutions. Ferric chlorid was an inferior source 

 of iron, and dialyzed iron utterly inadequate. Only ferric tartrate 

 furnished sufficient iron in the alkaline Solution. 



Plants grown in the acid Solutions contained the highest per- 

 centages of iron. Plants grown in the neutral Solutions contained 

 higher percentage of iron than those grown in the alkaline Solutions 

 when some forms of iron vvere used, but equal percentages when 

 other forms of iron were used. The percentages of nitrogen, phos- 

 phoric acid, lime, magnesia, and carbon free ash in plants grown 

 in six different Solutions did not vary appreciably when compared 

 with the iron content. 



It was evident that rice was not particularly sensitive to the 

 reaction of the Solution, except as the reaction infiuenced the avai- 

 lability of the iron. This substantiates previous work in showing 

 that lime induced chlorosis is caused by a lack of iron and indica- 

 tes strongly that the only action of carbonate of lime in inducing 

 chlorosis lies in diminishing the availability of the iron. 



The amount of available iron in the different Solutions could 

 not be determined analytically, because of the impossibility of dis- 

 tinguishing between colloidal and soluble iron. Calculations showed, 

 however, that the concentration of available iron in many cases 

 must have been less than one part in 10,000,000 of Solution. 



Reference was made by the writers to the bearing of these 

 results on the proper composition of plant nutrient Solutions. 



M. J. Sirks (Wageningen). 



Gile, P. L. and J. O. Carrero. Immobility of iron in 

 the plant. (Journ. agr. Research. Washington. VII. p. 83—87. 

 1916.) 



Researches made by the writer on the assimilation of iron by 

 certain plants, have afforded results which seem to show that iron 

 is relatively immobile in the plant after it has once been trans- 

 ported to the leaves. In respect to mobility in the plant iron would 

 thus be similar to Silicon and calcium and different from nitrogen, 

 phosphorus, potassium, and magnesium, which are generally con- 

 sidered mobile. 



Rice growing in a nutrient Solution well supplied with iron and 

 then transferred to a Solution identical except the absence of iron, 

 formed during growth in the complete nutrient Solution dark green 

 leaves, while the leaves that formed after change to the iron-free 

 Solution were 57^ellowish green to creamy- white, the old leaves 

 retaining their dark green color during this change. 



Phenomena similar to that observed in rice grown in iron-free 

 Solutions were observed with rice and pineapples {Ananas satwus), 

 grown in calcareous soils. Rice when not immediately affected with 

 chlorosis showed the chlorosis in the new leaves, even though the 

 old leaves were green. 



Rice plants grown in certain nutrient Solutions with a lack of 

 available iron developed chlorosis; tips of leaves just emerging from 

 the stalk were brushed with a 0,2 to 0,4 per cent Solution of fer- 

 rous sulphate; these leaves growing out, the part that had been 

 brushed was a normal green, while the lower, unbrushed parts 



