26o 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
In most cases, the quantity of plant material produced was too small 
to permit the analysis of the grain and straw for all the essential nutrient 
elements limited in the cultural series; therefore, it was necessary to select 
certain of these plant constituents which would represent elements having 
a very definite chemical combination with many of the complex plant 
substances, and certain others whose action was more or less secondary in 
nature. Phosphorus and calcium were finally selected, and determinations 
were made for total phosphorus and calcium present in the oat grain and 
straw. 
Analytical Methods 
The well matured grain and straw were ground to a finely powdered 
mass after drying at 90° C. for 12 hours, and stored in tightly stoppered 
ibottles for analysis. After the samples were dried to constant weight at 
110° C. and thoroughly mixed, samples were weighed out for calcium and 
phosphorus determinations. Two-gram samples for grain and one-gram 
samples for straw were taken for the calcium determinations, and one-gram 
samples of both grain and straw were used for phosphorus determinations. 
The official analytical methods as set forth in Bureau of Chemistry 
Bulletin 107, or standard methods which had been carefully checked with 
the "official methods," were employed in all cases. 
All analyses were run in duplicate, and, in case they did not check within 
0.5 percent, were repeated. In the cases of three samples, however, of 
which there was insufficient material, only one sample was analyzed. The 
results given in the tables are averages of these duplicate, or in some cases 
quadruplicate, determinations. 
The samples for calcium determinations were ignited at low heat in a 
muffle until completely ashed, digested in hydrochloric acid, and finally 
filtered. Calcium was precipitated as calcium oxalate after removing the 
hydroxides of iron, aluminum, and phosphorus, and determined as CaO by 
titrating the oxalic acid with standard potassium permanganate. 
The phosphorus samples were analyzed by the sodium-peroxide method 
as originally described by Osborne (1902) and modified by Dubois (1905). 
The sample was placed in a nickel crucible and moistened until it formed a 
thick paste, after which five grams of anhydrous sodium carbonate were 
added and the charge was mixed immediately. Five grams of sodium perox- 
ide were then added in smaller portiolns at a time with thorough mixing 
after each addition. The mass was then heated until fusion was complete. 
Additional sodium peroxide was added to oxidize completely the organic 
matter. The mass was dissolved in concentrated hydrochloric acid, made 
up to 250-cc. and loo-cc. aliquot portions used for phosphorus determina- 
tions. These lOO-cc. samples were evaporated to dryness over a water 
bath, taken up with hot water, strongly acidified with nitric acid, and 
phosphorus was determined by the "official gravimetric method." 
