262 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
These samples were rather small, however, and therefore the data are not 
as accurate as desired. The calcium content of the grain from the phos- 
phorus- and nitrogen-deficient solutions for the last year (191 7 column, 
table 4) in which the total number of plants was greatly increased, making 
more material available for analysis, is considerably lower than in any of the 
other samples. The data for these last two series, namely, phosphorus- 
and nitrogen-deficient cultures, are too varied to draw any conclusions. 
In the case of the other samples, however, it is quite evident that a marked 
variation in the nutritive solution produces a very considerable change in 
the calcium content of the grain. 
It is held by some that calcium and magnesium function in the trans- 
location of carbohydrates and proteins and in the storage of these compounds 
during seed formation, rather than being directly connected with the syn- 
thesis of the carbohydrates and proteins that are later transferred to the 
seed. Calcium probably functions in this capacity much less than does 
magnesium, as analyses show a scarcity of calcium and an abundance of 
magnesium in most seeds. Magnesium probably functions, therefore, as 
the chief carrier of phosphoric and other acids entering into the chemical 
composition of the seed, while calcium acts more as a neutralizer of acids 
resulting from synthesis. Bernardini (1914) describes quite fully the 
functions of magnesium and its probable relation to translocation processes. 
This indirect function of calcium was first pointed out by Holzner (1867) 
and Schimper (1890), and more recently. has been supported by Chirikov 
(1914), Robert (1917) and others. 
Truog (1916) states that plants with a high protein content generally 
have a high calcium content and that when manganese phosphate is used 
instead of calcium phosphate as a source of phosphorus the plants grown in 
such a solution have an extraordinarily high manganese content. Robert 
(191 1, 1912) attempts to show that calcium is deposited directly within the 
fungus as a calcium salt of certain organic acids. She shows that an in- 
crease of calcium in the culture solutions results in a very marked rise in 
the calcium content of the fungus. 
In general, a deficiency of calcium in the nutritive solution results in 
the production of grain with a very low calcium content, while on the other 
hand a deficiency of magnesium or of potassium in the culture solution causes 
a slight accumulation of calcium in the grain of the plants grown therein. 
The effect of a deficiency of either phosphorus or nitrogen generally results 
in the production of grain with a low calcium content. The calcium content 
of the grain of oat plants grow^n under varied nutrient conditions is consider- 
ably altered by the composition of the nutrient solutions in which the 
plants grow. 
