Journal of Agricultural Research 
Vol. XXIII, No. 3 
158 
to germinate at 19 0 C. after cold storage in the fruit until May 7, 1919, 
followed by removal from the fruit and incubation in the ice box for 
about a week. With the outer coats removed 67 per cent germinated 
in 3 days and 100 per cent in 6 days; with the outer coats left on 26 per 
cent germinated in 3 days and about 50 per cent in 6 days. 
The effect of the removal of the seed coats from seeds which have 
previously been incubated for a considerable time at temperatures un¬ 
favorable for after-ripening, and which are still incapable of germinat¬ 
ing in intact condition is of special interst, Seeds of the cider press 
lot, which had remained dormant under germination conditions for 6 
months—4 months with outer coats removed—all germinated in 3 days 
after removal of the inner seed coats. 
With intact York Imperial and Newton Pippin seeds, which had been 
dormant under germination conditions for more than 5 months and more 
than 2 months, respectively, the respiratory intensity was increased 
more than four-fold in 24 hours by removal of the outer seed coats. The 
inner seed coats were then removed and all of the seeds germinated in 
the next 2 days. It is evident that these embryos were in a very differ¬ 
ent condition when freed from the coats than were the embryos of 
the cider press lot which were freed from the coats soon after putting to 
germinate 6 months earlier, and which then failed to germinate. Yet 
as far as ability to germinate with the coats on is concerned they showed 
no difference. There is here a joint action of the coats and of the con¬ 
dition of the embryo in imposing dormancy, whereas in the dry-stored 
seeds the same result is produced without the coats. It seems, therefore, 
that some part of the complex of processes which constitute after-ripen¬ 
ing must go on both at the higher temperatures and at the after-ripen¬ 
ing temperatures. Apparently other processes, perhaps consisting es¬ 
sentially in the removal of inhibitors to germination (which can also 
be dissipated or oxidized upon removal of the coats) take place only at 
the lower temperatures. 
In this connection Kidd’s work (14) on C 0 2 and Maze’s (20 , 21) on 
acetic aldehyde as inhibitors to germination are of interest. Experi¬ 
ments show that there is a free interchange of oxygen and C 0 2 responding 
in characteristic ways to differences in temperature, in the respiration 
of dormant apple seeds. This makes it seem unlikely that inhibiting 
concentrations of C0 2 accumulate within their coats. That some other 
inhibiting substance is produced at higher temperatures and is held in 
in by the coats, or else, being initially present, is removed at lower tem¬ 
peratures, seems more plausible; but no work was done to test the valid¬ 
ity of such an assumption. 
An alternative hypothesis is Kidd and West’s conception (15) of a 
mechanical stimulus according to which dormant white mustard embryos 
are considered as in a state of very delicate equilibrium from which they 
are aroused to activity by the mechanical shock resulting from removal 
of the coats, without reference to any causal chemical change. 
The inner seed coats are very effective in preventing decay of the em¬ 
bryos during the after-ripening, whereas the thick hard outer seed coats 
with their open hila are of little value in this respect. This was shown by 
seeds of the cider press lot, many of which had been so injured that it 
was impossible to prevent severe decay in the incubator even after care¬ 
fully discarding all seeds showing visible injury and surface sterilization 
of the remaining seeds. After 50 days’ incubation at 20°, 25°, and 
