Avams—HEffect of very low Temperatures on Moist Seeds. 3 
must have been intercepted by the imperfect conducting power of 
the seed-coats.”’ Both these statements can scarcely be true. As 
heat and cold are varying degrees of the same thing, it does not 
appear evident why the seed-coat should conduct the cold in the 
one case, and refuse to conduct the heat in the other. However, 
to test the matter I made the following rough experiment. An 
ordinary cork, one inch in diameter, and a number of dry bean- 
seeds were put into a test-tube and kept at a temperature of 
100° C. for less than half an hour. They were then taken out and 
split in two, with the result that the interior of the bean-seeds was 
hot enough to burn the fingers, while the inside of the cork was 
also decidedly warm; but the latter was a much less efficient 
conductor of heat than the beans. 
Assuming, then, that the seeds did eventually come to the 
temperature of the liquid air or liquid hydrogen, were they, there- 
fore, frozen? Air-dried seeds contain about 12 per cent. of 
moisture, and there is little doubt that freezing, that is, a forma- 
tion of ice particles, did not take place. it would be as reasonable 
to think of freezing a dry piece of wood or a handful of hay. 
Probably the only change that resulted was a slight contraction of 
volume; but, in the absence of experiments, it is impossible to say 
how much this contraction amounted to. 
It remains to consider the behaviour of the gases in the inter- 
cellular spaces. ‘These are probably nitrogen, oxygen, and carbon 
dioxide. As the temperature gradually falls, these gases will 
doubtless be liquefied—assuming that the seeds have been immersed 
in liquid hydrogen. A vacuum will result, but the total pressure 
—allowing 15 1b. to each square inch of surface—would be so 
small as to have no appreciable effect on the seed. The actual 
figures for one example may be quoted. Theseed of swede turnip 
is spherical in shape, and has a diameter of 1} mm. The area of 
its surface will, therefore, be about , of a square inch. If a 
vacuum is formed inside the seed, the total pressure on the seed will 
be about 4 of a pound (taking the atmospheric pressure at 15 lb. 
to the square inch). Now, according to Scott-Hlliot’s results,' the 
total force required to crush turnip seed is about 13 lb.; that is, a 
force nine times as great as that due to the formation of a vacuum. 
1 «¢ Nature Studies—Plant Life,’’ p. 80 (1903). 
