54 
AMERICAN JOURNAL OF BOTANY 
[VoL 9 
Cereal Investigations of the United States Department of Agriculture for 
the suggestion of the problem and for much valuable information. Dr. 
Alice M. Russell has. added greatly to the interest of the investigation by 
her mycological study of the discolored nodes. To Dr. R. H. True and to 
other members of the Botanical Department of the University of Pennsyl- 
vania, the writer is greatly indebted for generous help and criticisms. 
Table i. The Efect of the Composition of the Nutrient Solution upon the Availability of 
Iron in Ferric Phosphate 
Solution 
Mg. FeP04 
Total Weight 
Relative Weight 
per 
Liter 
Tops 
Roots 
Tops 
Roots 
"H" 
7 
82.6 gm. 
344 " 
43-9 " 
59-84 " 
3.84 gm. 
2.24 " 
2.3 " 
3-68 " 
100% 
42% 
53% 
72% 
3 00% 
58% 
59% 
97% 
"A" 
3-5 
H 
35 
"A" 
"A" 
Experimental Data 
I. The Effect of the Composition of the Nutrient Solution Upon the Avail- 
abiUty of Iron in Ferric Phosphate 
Four cultures were set up in duplicate as shown in table i. The'plants 
were grown in the 800-cc. jars during the period from February 7 to March 
5, 1 92 1. The "H" solutions were changed twice a week; the others every 
7 /4 0.0000s 0.0001 o.oooz 0 000s 0.001 0.0000S o 000s o.oof 0002/V 
mgm.perZ.F^ PO4 ' FeSO^ ' TeiJ^O^)^ 
Fig. I (left). Relative growth of roots and tops with FeP04 in solution "A" (3.5, 
14, 35) and "H" (7). 
Fig. 2 (right). Relative growth in solution "A" with FeSO^ and Fe(N03)3. Also 
H-ion concentration before and after growth. 
