210 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
The openings do not appear to have been related to the presence or absence 
of any chemical element or salt in the solution. But wheat roots failed to 
exhibit these cortical openings when grown in sand or soil for 13 days at 
summer greenhouse temperature. Whether wheat may be expected to 
show these openings always when grown in liquid media, and whether it 
may sometimes show them when grown in soil or sand, remain open ques- 
tions. 
Turning to the observations on Indian corn, during the months of 
January, February, and March the white dent variety was grown in many 
different solutions (with from one to five salts), and cortical openings were 
regularly developed in roots that had reached a length of 10 or 12 cm. 
Plants of the same variety grown in moist, rich garden soil within the same 
period uniformly failed to show openings in roots 10 to 18 cm. in length. 
In June, Shive's solution R4C5 (sub-optimal series) produced openings 
like those shown in figure 3. The seeds had been germinated in sphagnum 
(i5°~35° C.), and the seedlings had been in the solution (20°-35° C.) for 
only 70 hours. The openings were present to within about 3 cm. of the 
tip of the root. At about the same time similar results were obtained with 
distilled water and with single salt solutions (0.00048 normal) of Ca(N03)2 
and Mg(N03)2. Apparently the liquid media produced the same growth 
response in these roots in summer as in winter. 
With soil and sand cultures, however, the results obtained in June were 
somewhat different from those recorded for the winter and early spring. Corn 
plants that had grown 12 days in moist, rich garden soil (greenhouse, 20°- 
40° C.) showed many cortical openings, even to within 3 cm. of the tip of 
the root (fig. 3). The openings in the older portion of the root appeared 
very large in cross section and were about 8 cells in length. Perfectly 
parallel results were obtained with moist sand cultures at the same time. 
White dent corn seedlings that had been grown in sphagnum (in the 
greenhouse) until the roots were 10 cm. long showed pronounced openings 
in the older portions of the root (to 4 cm. below the seed) when the test 
was made in June, but showed no openings in the case of similar tests made 
in the winter months. 
It appears that cortical openings were regularly formed in white dent 
roots more than 10 or 12 cm. in length, grown in liquid media, whether in 
winter or in summer, and they also appeared in roots 12, 14, or 16 cm. in 
length, grown in soil, sand, or sphagnum during a period of high tempera- 
tures in the summer. The rate of growth of the root rather than the age of 
the seedling seems to be the factor determining the time of appearance of 
these openings. It is at once suggested that temperature and oxygen 
supply may be among the environmental conditions influencing the phenom- 
enon in question. It seems safe to suppose that roots grown in sand, soil, or 
sphagnum generally have better opportunity for absorbing oxygen than 
those grown in liquid media, and this consideration may possibly furnish 
