VALUE OF CERTAIN NUTRITIVE ELEMENTS 
around each plant and a paraffin seal run over the top of the moist 
sand. The tubes were then plugged with cotton to prevent evapora- 
tion from the space not occupied by the stem, and the jars were placed 
in position under the open greenhouse. 
The solution in the culture jars was maintained as nearly as possible 
at 60 percent of the moisture-holding capacity of the sand, the pots 
being brought to their former weight by pouring the culture solution 
through the glass tube into the inverted funnel. The jars were aerated 
by forcing air through this watering tube once a week. 
The plants were grown under these conditions until completely 
matured, a period of about ninety days, from May until August, 
each year. Frequent observations were made and careful notes taken 
of the development until the plants were well ripened, when the final 
data were obtained. In all cases, the essential data are given in the 
following tables or in the text in connection therewith. The results 
given in the tables are averages of a series of checks. The number 
of determinations is given in each instance, with the mean variation 
following. Peters's abridged method (Briggs and Schantz, 1914), 
based upon the sum of the departures from the mean, was used to 
calculate the probable error of the mean as given in the formula 
in which Rm = the probable error of the mean, 1>d the sum of the 
departures, and n the number of determinations. 
The Relation between Nutrients and Growth 
The effect of limiting the essential mineral elements becomes 
apparent soon after the seedlings are transplanted. The plants grown 
in the solutions deficient in magnesium or in calcium stool heavily 
five days before those grown in the normal solutions. Those grown 
in potassium-deficient solutions, on the other hand, produce plants 
which stool slightly less heavily than the plants in the normal solutions. 
Each seedling in the solutions deficient in phosphorus or in nitrogen 
produces but one slender shoot. 
The general appearance of the plants is markedly affected even 
before stooling begins, and during the subsequent development very 
Rm = 0.845 
I 
