46 BOTANICAL GAZETTE [JANUARY 
not to changes in the permeability of the coat, as later ieee: 
show. 
Table XII gives the changes of H* ion concentration as P, 
values for the endosperm and different parts of the embryo during 
storage at 5° C. The outer cells of the embryo and its hypocotyl 
were the first parts to show an increased H* ion concentration. 
TABLE XI 
PERCENTAGE OF WATER IN SEEDS TAKEN FROM COATS AFTER 
DIFFERENT PERIODS OF EXPOSURE TO - 
Seeds Percentage water 
Dag e tina N Clow eat Ep eo eae chek uke cas .19 
After: coave stg) Ce oe ie Conk ae es 24.84 
After: (6 0aye at se a 23.34 
AEE FOCavE SES (3. > le ea ee fore) 
miter ON Uaye OE Ci ee a 3.00 
a CAVE RE ee ae es 23.21 
oo days at 5° C. (coat splitting open)....... 52.64 
cae eK days at 5° C. (seedlings 25 mm. long)... . 88.38 
TABLE XII 
H+ION CONCENTRATION OF SEEDS DURING AFTER-RIPENING* 
Condition Part of seed PB, 
DIV se ee ee ae Endosperm 4.4-0.0 
ee ee ek ee ca es bryo 8.4-8.8 
ter 40 days at © ©. . 2. vee. Endosperm 4.6-5.2 
Alter 30 Give st oo Ce bryo 6.8-7.6 
tet Gorinyaat € Ooo. ces Endosperm 4.4-6.0 
After 60 days at ¢ GC. 51. Embryo 6.8-7.6 
miter O60 Gaye at © OC. Embryo hypocotyl 6.0-6.8 
After oo daye at x° Ci. oo eee Endosperm 4.475.2 
t WeOt oO. cco Embryo outer cells and je aes 4.4-§-2 
After 60 daybet- eC. ca ee, Embryo inner cells 4.6-6.0 
*Th determinati were made with the Clark and Lubs indicators. 
The embryo showed a marked increase of H* ion concentration dur- 
ing after-ripening, while the endosperm with P,, value of 4.4 (con- 
centration of H* ions x N =o.72 107‘), being already acid, showed 
very little change. This may indicate that the embryo is the 
principal seat of dormancy. Table XIII gives the increase of 
titratable acid in the endosperm and embryo during after-ripening. 
The increased acid was determined by titrating with N/50 NaOH, 
