56 
N. C. Experiment Station 
ROLE OF THE SEED COATS 
When Lipscomb and Corley 43 -heated cotton seed in a vacuum or in an 
inert gas like nitrogen at 100° for 26 hours, they obtained a higher per¬ 
centage of germination in treated than in untreated seed. Other workers as 
Haberlandt, 20 Wiesner 02 Velten, 00 Honing, 35 Davis, 12 Harrington 30 and others 
found that certain heat treatments accelerated germination or increased 
the total percentage of germination or both. In a number of the germina¬ 
tion tests conducted by the writer, cotton seed which had been given certain 
treatments with dry heat appeared to germinate more rapidly than untreated 
seed. In order to determine whether this increase in rate of germination 
is due to some wholesome effect of the treatment on the embryo or whether 
it is due to some favorable change in the seed coat, certain experiments 
were planned. The results of these tests are set forth in Table V. 
In experiment 1, four lots each of 100 seeds of the 1923 crop w^ere 
used. The seed were carefully selected in order to have the different 
lots as uniform as possible. Lots 1 and 3 were dried at 60° for 18 hours, 
then heated at 95° for 12 hours. Lots 2 and 4, which were neither dried 
nor heated in any way, were used as checks on lots 1 and 3. The seed 
coats were removed from lots 1 and 2 and the embryos were put to germ¬ 
inate while the seeds of lots 3 and 4 were put to germinate with testas 
intact. The seeds were germinated between sterile blotters in pans hold¬ 
ing 50 seeds each. Since each lot was germinated in two pans the method 
involved a check on such irregularities of germination that might obtain 
between one pan and another. Only the combined germination in the 
two pans representing each lot is given in the table. The number of seeds 
which had germinated was determined at the end of 25, 45, 57, 76 and 91 
hours, and the average length of the radicles (hypocotyl and tap root) was 
determined at the end of the 72-hour period for the seedlings whose testas 
had been removed and at the end of the 91-hour period for the seedlings 
whose testas had been left intact. Only seedlings whose root and hypocotyl 
were healthy were measured, the number of measured seedlings being given 
in the table. 
When the results of the tests with lots 1 and 2 are compared, it is seen 
that the embryos of treated seeds germinate more slowly than those of 
untreated seeds. At the end of 25 hours in the germinator only 62 treated 
embryos had germinated while 91 of the untreated embryos had begun to 
grow. At the end of the 45 hour period the germination was 88 and 99 
respectively for the two lots and at the close of the 76 hour period the 
comparison was as 93 to 99. At the end of 76 hours, the radicles of the 
treated seeds were 26.3 mm. long while those of the untreated seed were 
38.3 mm. in length. It is evident both from a comparison of the number 
of seeds which had germinated at a given time and a consideration of the 
average length of the hypocotyls that the treatment affected the embryos 
in such a way as to retard their rate of germination. The difference in 
the average length of the hypocotyls of the two lots does not appear to be 
due to more rapid growth of the untreated seedlings for measurements 
made on seedlings from treated and untreated embryos in lots 1 and 2 
of Experiment 2 described below, at the ends of the 72 and 112 hour periods 
show slightly greater gain in length of the seedling from treated seed. 
