212 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
burettes and diluted to the required volume with water that had been con¬ 
densed in block tin and stored in a paraffin-lined jar. 
Table i. Composition and Hydrogen-ion Concentration of Solutions Employed 
Solu¬ 
tion 
Num¬ 
ber 
Shive’s 
Designation 
Hydrogen-ion 
Concentration 
pH 2 
Composition 
Partial Concentration in Grams per Liter 
of Solution 
kh 2 po 4 
CaN0 3 .4H 2 0 
MgSO4.7H.2O 
1. 
R2C4 
3-94 
0.98028 
2.45600 
4.92984 
2. 
R4C3 
3-85 
1.96056 
1.84200 
3.69738 
3 . 
r 5 c 2 
3.68 
2.45070 
1.22800 
3-69738 
4 . 
r 6 c 2 
3.60 
2.94084 
1.22800 
2.46492 
5 . 
RgCi 
3-47 
3.92112 
0.61400 
1.23246 
3 drops of a o.ooi M solution of Fe 2 Cl6 were added to every 325 cc. of nutrient solution. 
The seeds were germinated on moist, unglazed pottery, and were then 
placed on paraffined cotton netting stretched over the tops of glass tumblers 
of tap water, where they remained for three or four days, or until the seed¬ 
lings were from four to six centimeters high. From these, plants were 
selected for uniformity in size, color, and development, and were transferred 
to culture bottles containing the nutrient solutions, which were changed at 
intervals of from three to five days. The culture bottles were of flint glass, 
with wide mouths and cork stoppers, and had a capacity of about 325 cc. 
Each was enclosed by two jackets, the inner one of heavy black paper, the 
outer one of heavy light-colored manila paper. Four holes were bored in 
each stopper, which was then immersed for a few minutes in hot paraffin, 
and one plant was fixed in each hole with a pledget of non-absorbent cotton. 
The cultures were kept in a greenhouse at a temperature of 20° to 25 0 C. 
throughout the winter and spring months. 
Although differences in the length and general appearance of the plants 
were not noticeable during the first few days that the plants grew in the 
nutrient solutions, there were appreciable differences in the root systems 
before the third day. The roots of plants in solution 1 were long and straight 
with several long secondary roots; those in solutions 4 and 5 were short 
and stubby. Some of the roots in solution 5 were branched very near the 
tips; these branches were hardly more than tubercles. The secondary roots 
in solutions 4 and 5 were thick, much branched, and bore an unusually 
large number of root hairs, some of which were so long that their ends 
projected beyond the tip of the root itself. Plants in solutions 2 and 3 
presented appearances intermediate between the two extremes; the roots were 
of medium length and were moderately branched, but they were not stubby. 
At the end of a week the differences between cultures were even more appar¬ 
ent. It thus appears that short, stubby, branched root systems are associ- 
2 These pH values are somewhat smaller than those obtained by McCall and Haag 
(’20) and by Meier and Halstead (’21). However, since it is the relative concentrations 
that are of value in the present experiments, the actual pH is unimportant. 
