Page:Popular Science Monthly Volume 51.djvu/116

108 cover of a wooden box in a compressed-air refrigerator for meats, where they were exposed for a hundred and eighteen days to repeated but not continuous refrigerations, most of which lasted twenty hours each. The lowest temperature reached was −53·89° C. (−65° F.); the highest, −37·78° C. (−36° F.); and the mean, −41·93°C. (−43·4° F.). After each refrigeration the temperature rose to that of the interior of the receiver, but slowly, while the refrigerations were rapid.

After the conclusion of the experiment, when taken out of the refrigerator and planted, the wheat, oats, and fennel came up promptly; only thirteen out of sixty seeds of sensitive plants germinated, and of lobelia seeds, which were too small to be counted, only ten. The failures of the sensitive-plant seeds could not all be attributed to the cold, for others of the same species which were not refrigerated did but little better. The lobelia seeds were, however, certainly killed by the cold, for the control seeds germinated abundantly. It is safe, too, to infer that seeds can remain inert and unharmed in a medium unsuitable for respiration, provided nothing is present to injure their protoplasm through chemical action. Such a medium, for example, would be an atmosphere of carbonic acid.

I desired to ascertain the effects on germination of keeping seeds in vacuum. The most obvious way of trying this experiment, by the formation of a barometrical vacuum, was liable to the objection that the abrupt removal of the air and moisture might disturb the tissues and modify the structure and composition of the protoplasm of the seeds, and thereby produce a complication of results. I therefore tried another way, by immersing them in mercury under such precautions that no air could reach them other than what they contained within themselves. The results agreed substantially with those obtained by refrigeration, and go to confirm the view that seeds can continue to subsist in a condition of complete vital inertia, from which they recover whenever the conditions of the surrounding medium permit their energides, or the living masses of their cells, to respire and assimilate.

At first sight, this return to life resembles the resumption of motion by a machine that has been resting when it is put into communication with its motor—a comparison which has been often made. But the phenomena are not of the same nature in the two cases, and the energides, of which the total constitutes the living individual, are not machines in the usual sense of the word. For a machine works without changing its structure, while the energides segmentate after they have grown, and their segmentations operate in their turn as energides. This is because the matter assimilated by living protoplasm augments its mass