a ee 
44 BOTANICAL GAZETTE [JANUARY 
no germination, but some of the latter germinated after about 
6 months. While exposure to —5° C. was not sufficient to injure 
the ungerminated seeds, it proved fatal to the germinated seeds. 
This is due to the fact that when the coat splits open the endosperm 
and embryo just doubles its water content and thereby dilutes the 
cell sap to a degree which permits ice crystals to form. Seeds at 
this period and later periods of development were killed by expos- 
ure to —5° C. for seven days or less. The after-ripening and gain 
in catalase activity was a little more than enough to account for 
the sum of the effect at'5° C. These results show that the alterna- 
tion of temperature between —5° and 5°C. had slight forcing 
action. This forcing action is equal to that obtained by keeping 
seeds in running water at 10°C. It is also evident that seeds ready 
‘to germinate should not be subjected to —5° C 
The early changes taking place in seeds put to germinate at 
o+1°C. were similar to those at 5° C. except for being retarded. 
At this temperature the increase in catalase activity was very 
much retarded, although it was over 3 times that gained by seeds 
stored at —5°C. per unit time. These seeds were studied as to 
storage material, H* ion concentration, and permeability, and 
found in good condition. The Juniperus seeds not only after- 
ripened but germinated at o#1°C., even though it required 5 
or 6 months. 
yMoist seeds were placed at 5°C. for germination. At this 
/Aemperature the catalase activity increased most rapidly. The 
physiological changes occurring in the seed at 5° C. were most 
rapid, and will be discussed in detail under changes preparatory to 
germination. This constant temperature of 5° C. also gave rise 
to by far the largest percentage of germination, and the most 
. vigorous seedlings. 
“~~, It is evident from these germination experiments that: (1) tem- 
peratures above 10° C. and below o° C. are not favorable for after- 
ripening and germination; (2) no one of the forcing agents as 
used was of value in germination; (3) the inclosing structures do 
not inhibit germination; (4) but the inhibiting conditions are 
to be found in the endosperm and embryo. ‘These facts indicate 
that the juniper seed has a dormant embryo that must go through 
