1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 7 
supplied from the Plant Introduction Garden of the Bureau of 
Plant Industry at Chico, California. The latter had been found 
by Dr. H. S. Reed to be particularly good for solution culture 
work, and my experience is entirely confirmatory. The other 
seed were from selected but unnamed field varieties. 
The seed were immersed over night in running water, and 
then the peas and corn placed for germination on paraffined wire 
netting over pans of well-washed, moist sphagnum. They were 
covered with moistened paper toweling, over which was inverted 
other pans, though ample ventilation was provided. The wheat 
was treated in much the same way except that it was germinated 
over water frequently changed. As soon as the plumules 
emerged light was admitted. After properly placing the seed- 
lings, ten to each tumbler, they were left in diffuse light, in the 
room in which set up, for 12 to 24 hours in order to become 
better adjusted to the conditions before being installed in the 
greenhouse. 
In some of the earlier experiments a complete series was 
arranged under a single set of conditions, and in such cases the 
tumblers were placed upon a rotating table. In much of the 
later work, however, more than one set of conditions was in- 
volved, so that the use of rotating tables was not practicable, 
and under the circumstances special care was taken with prop- 
erly placing and spacing the tumblers on lattice tables, likewise 
shifting the order of the cultures so as to be wholly comparable. 
In all cases as the plants were harvested, the remains of the 
seed, or cotyledons, were cut away. This was found necessary 
inasmuch as otherwise a considerable error would be introduced 
in the weights of those cultures in which relatively little growth 
occurred; for it was in such plants that the seed were incom- 
pletely exhausted. On removal from solutions containing 
precipitates the roots were thoroughly washed, and in all cases 
quickly and uniformly dried of surface water on absorbent gauze. 
The criterion of growth on which stress is laid in this paper 
was total green weight. Other data included green weight of 
tops, average length of shoot (or leaf), dry weight, and general 
appearance—including root characteristics. Total green weight 
is, for the present purpose, entirely satisfactory and has the 
advantage in these relatively short-interval cultures of expressing 
