276 BOTANICAL GAZETTE [OCTOBER 
This involves the necessity of making a study of the respiratory 
ratios at 19° and at 33°, both with the coats intact and removed. 
Table VI shows the effect of high temperatures on the respiratory 
ratios when the seed coats are intact. In this experiment equal 
weights (2.688") of seeds of X. echinatum were used in each case. 
The results are therefore comparable in every way. It is seen that 
at 33°, up to the 6-hour 50-minute reading the respiratory ratio for 
both upper and lower seeds is 1. After this reading the ratio falls 
rapidly, reaching at the 12-hour reading 0.82 in the case of the lower 
seeds and 0.87 in the case of the upper ones. It was observed that 
soon after the 6-hour 50-minute reading the radicles began breaking 
through the seed coats. In a large number of experiments at a3 
the respiratory ratio always fell rapidly after the radicles broke the 
seed coat. At 19°, with the seed coats intact, the respiratory ratio 
is 0.6 in the lower seeds and 0.64 in the upper ones. Many measure- 
ments at 33° with seed coats removed showed a respiratory ratio of 
o.7—-0.8 in both the upper and lower seeds, while numerous measure 
ments at 19° with seed coats removed always gave a respiratory ratio 
of about 0.6. 
- The facts may be summarily stated thus: the respiratory ratio 
with the seed coats removed is about 0.6 at 19° and o.7-0.8 at 
33°; with the seed coats intact it is 0.6 at 19° and 1.0 at 33°. From 
these results two conclusions are plain: the respiratory ratio rises 
considerably (from 0.6 to 0.8) with a rise in temperature from 19° 
to 33° under the free oxygen supply secured by the removal of the 
seed coats; but it rises much more (from 0.6 to 1.0) with the same 
TABLE VI. 
X. echinatum—sEED COATS INTACT; 119 UPPER SEEDS; 88 LOWER; 2.68 GM. 
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