362 
Journal of Agricultural Research 
Vol. XI, No. 8 
readily formed upon adding magnesium mixture to certain parts of the 
tissues. 1 
Repeated examinations for the relative abundance and for the first 
appearance of the crystals showed that they decreased in the order of 
the following locations: Taproot; bundles, and surrounding tissues near 
where the taproot merges into the thickened root; inside the cambium 
in the more active xylem tubes and surrounding parenchyma; outside 
of the cambium layer in the cortex; medullary rays, decreasing inward; 
and, finally, only traces in the pith and leaf petioles, from which it dis¬ 
appeared first upon again withholding phosphorus from the nutrient 
solution. The turnips which received maximum phosphorus nutrition 
increased to from 3 to 4 inches in diameter while growing in the solution. 
It was noticed, while following the progressive decrease and increase 
of phosphorus directly precipitable by magnesium*mixture that there was 
the opposite condition concerning the amount of starch. Simultaneous 
with an increase in the absorption of phosphorus it was observed that the 
leucoplasts containing the compound starch grains shrunk in size as the 
starch grains were corroded and dissolved, until finally when the maximum 
amount of phosphorus had been introduced into the nutrient solution, 
starch had practically all disappeared from the root tissues only to re¬ 
appear when phosphorus was again withdrawn from the nutrient solution. 
Similar observations have been made at this station (5) concerning 
starch, especially in potato vines growing with widely differing amounts 
of various nutrients, and it seems probable that a retardation in growth 
and in consequent carbohydrate requirement, owing to suboptimum 
nutrient conditions, tends toward an increased deposition of starch, 
although it is possible that the nutrients may serve as activators of 
amylases. 
Examinations for precipitable phosphorus in the tissues of turnips 
grown under natural conditions in soil containing varying amounts of 
available phosphorus have been recorded previously (6). They furnished 
indications that the extent to which crystals were produced in the 
tissues upon treatment with magnesium mixture varied to a certain 
extent with the amount of available soil phosphorus. 
Owing to the fact that the greater part of the phosphorus in turnips 
exists in the cell sap, the principal work now to be recorded deals with 
the soluble phosphorus. Some observations based upon the preliminary 
work have been made already in another connection (8). 
1 The principal features of the anatomical structure were found to be as follows: The taproot and, at the 
early stage, the thicker portion above it are diarch. As the plant develops the latter portion becomes 
collateral. The root portion finally consists of radial rows of bundles of vessels surrounded by fibrous, 
sharp-pointed cells between which the parenchymatous medullary rays are located. The remaining 
central area consists of thin-walled cells of irregular shape and size, which usually contain much starch and 
perform the functions of a storehouse. At the locality from which the leaves come the vascular xylem is 
limited to a narrow area surrounding a distinct pith which contains no differentiated vessels. This extreme 
upper part of the so-called turnip root must be considered as the stem and is differentiated by its voluminous 
pith from the enlarged and fleshy root portion with which it merges. 
