636 
Journal of Agricultural Research 
Vol. XXXI, No. 7 
Since it was found impracticable, on account of fluctuating weather 
conditions, to obtain consistent results from seedlings selected on 
different dates, it is suggested that the data in Tables I, II, and III 
be studied and compared under one date at a time. 
The heaviest mortality occurred where the radicles were only 25 
millimeters long. In this stage the cotyledon was just pushing through 
the seed coat and only the primary root had emerged. The greatest 
number of plants survived from stages where the radicles had attained 
considerable length and wdiere the plumule had ruptured the tip of the 
coleoptyle. 
In testing the effect of different concentrations on the seedlings it 
was noted that a more rapid plumule growth often developed in con¬ 
centrations of 18,000 to 20,000 parts per million than in weaker 
solutions. It was discovered that this could be attributed to the 
rapid decay of the primary radicle and the prompt production of 
permanent roots to carry on the development. In order to test the 
rapidity of response to the destruction of the primary radicle, several 
comparisons were made between pan cultures of seedlings in part of 
which the radicles had been excised with a scalpel about 6 millimeters 
from the base of the mesocotyl and others which received no mutila¬ 
tion. The percentage of seedlings remaining alive after 72 hours in 
the salt solutions is given in Table II. 
Table II. — Percentage of maize seedlings with excised and normal radicles sur¬ 
viving after 72 hours in salt solution ( 22,000 parts per million) 
Apr. 6 
Apr. 14 
Apr. 21 
Date 
Percentage of seedlings 
surviving 
Radicles 
excised • 
Radicles 
not excised 
1924 
15.0i 2.41 
2.5±1.05 
* 
40.8±3.37 
14.8±2.41 
21.0db2.75 
5.7±1.62 
« Seedlings having radicles approximately 40 millimeters long were used, and approximately 100 plants 
of each treatment were used on the respective dates. 
The results in Table II seem to indicate that any form of injury to 
the primary radicles of the seedling stimulates the early production 
of permanent roots, and these latter appear to enable the seed¬ 
ling better to withstand salt solutions than do the primary roots. 
The results also indicate the necessity of strictly standardizing any 
method of testing seedlings for alkali resistance. It is obvious that 
any injuries to the seedling roots in handling might easily influence 
the number of plants selected as resistant where the growth of the 
plumule was used as a criterion. 
The behavior of the seedlings with excised radicles suggests that 
the apparent resistance exhibited by some very young seedlings 
whose primary radicles remained turgid with hardened bulbous tips, 
as previously described, may be of little significance as their response 
in growth when transferred to water was not nearly so rapid as the 
surviving plants with excised radicles. 
