16 ABSORPTION AND EXCRETION OF SALTS BY ROOTS. 
culture medium as ae Ca(NO,), alone. These facts are illustrated 
in Plate I, which shows one typical seedling from each of the 14 cul- 
tures, photographed at the end of the experiment. 
EXPERIMENT B. 
The series of cultures used in experiment B was identical with that 
of experiment A, except that the solutions were made up with water 
from the laboratory still. At the end of a week the results were the 
same as those obtained in experiment A. At the end of a month the 
cultures were in the following condition: 
M i ; 
No. 1 (000 MeN O3).). Roots dead; stem wilted; three (or only two) pairs of 
branches had developed successively in the axils of the cotyledons, of which all but 
the youngest pair were wilted. 
M 
No, 2 (599 Me(NOs)2). Root and stem dead; cotyledons alive, without axillary 
branches. 
No. 3 (oo Mg 5, a Ca). Roots well developed, living, but slightly discolored’ 
stem wilted above; one pair of axillary cotyledonary branches. 
Nos. 4 to 18. Roots like No. 3, but white; stem wilted above; no cotyledonary 
branches. . 
No. 14 (distilled water). Roots dead; plants much like those in No. 1, except for 
the presence of lateral roots. 
EXPERIMENT C. 
The first three cultures of the series used in experiment C were 
designed to determine the concentration at which magnesium nitrate 
alone exhibited an effect markedly more injurious than that of 
| iy M 
e . Te ° 
distilled water. No. 1 was distilled water; No. 2, 50,000 Mg 
(NO,).; No.3, eat Meg (NO,),. Cultures 4 to 14, designed to 
determine the highest ratio of magnesium to calcium which would 
permit lateral roots to develop perfectly, were of equivalent con- 
aa grading by tenths between cultures 2 and 3 of 
experiments A and B. The calcium concentration of each solution 
centration at 
s0b0 than that of the preceding solution, and the 
magnesium concentration correspondingly less. At the end of a 
week the plants had reached their maximum development. Nos. 
4 and 14 (the same as Nos. 2 and 3 of experiments A and B) showed, 
as the corresponding cultures in the previous experiments had shown, 
the striking contrast between a dead unbranched primary root and 
231 
was greater by 
