﻿Macloskie : Heat of Imbibition by Seeds 273 



the water has became compressed within the starch, and suggests 

 that the water first entering the starch undergoes the highest rise 

 of temperature, and therefore the greatest compression. Perhaps 

 the phenomenon is parallel with that of gases entering spongy 

 platinum or charcoal ; and there may be partial condensation as 

 well as compression of the imbibed water. Ganot states that the 

 ' humus ' is warmed in moist air by the imbibition of vapor, and 

 that plants are thereby benefited. (Ganot's Physics, § 482.) 



Neither Sachs, nor any other of the physiologists, so far as we 

 know, has applied this discovery to the case of germination. The 

 comparative freedom from water of ripe seeds has been usually ex- 

 plained as a protection from injury by exposure to extremes of 

 heat or cold, but it seems to be also in a certain way a reserve of 

 potential energy to be drawn on at proper time. 



In a rude experiment we placed dry peas with water in a bottle, 

 and beside it a < controul' bottle of water at the same starting 

 temperature. In about an hour the temperature of the first bottle 

 exceeded that of the second; soon the difference reached i° C, 

 at which it remained for three days, when some of the peas were 

 germinating. In a second experiment we used dry split-peas, de- 

 void of seed-coat, without radicle or plumule, where there could 

 be no germination. They absorbed the water quickly, but, as 

 ere was much loss of heat by radiation, they kept at a tempera- 

 ture only 1 ° C. higher than that of the control bottle ; thus for 

 fifteen hours, when they had become saturated, and the tempera- 

 ture fell to that of the other bottle. The difference of i°C. will 

 not appear insignificant if we reflect that Sachs made out a differ- 

 ence of only 1. 5 C. between the temperature of germinating peas 

 and that of the surrounding air. We may expect that the tem- 

 perature after germination, though produced in a different way, is 

 continuous in amount with the temperature before germination 

 caused by the imbibition of water, and that there is no jolt or gap 

 as to warmth in the transition from the dormant to the active con- 

 dition of the embryo. 



We have not attempted a quantitative estimate of the amount 

 of heat produced. This might be effected by taking the weight of 

 the seeds and the weight of the water, and finding how much ice 

 would be necessary to keep them down to the temperature of the 



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