MOISTUBE FATAL. 247 



be called life ; it must be merely chemical combination, with 

 aptitude for life." 



The prevailing opinion on this subject among physiologists 

 is, that germination can only take place when moisture, 

 warmth, and a free communication with atmospheric air are 

 simultaneously present. If so, then such cases as the preceding 

 may be explained by the absence of one or other of the three 

 conditions assumed to be indispensable, moisture, heat, and 

 communication with the air. 



The power of moisture exposed to the air, and in contact 

 with inert vegetable matter, such as a torpid seed, is by degrees 

 to produce decay, which rapidly spreads to the neighbouring 

 parts. But, if the vitality of a seed is excited by a fitting 

 temperature, the moisture with which it is in contact is then 

 decomposed, the oxygen so obtained combines with the carbon 

 of the seed, and forms carbonic acid which flies off, other 

 changes take place, and by degrees the matters lodged in the 

 tissue of the seed are brought into that condition which is best 

 suited for the growth of the embryo ; then, if the embryo is so 

 situated that it cannot obtain from the surrounding medium 

 food upon which to subsist, its germination stops, and its stable 

 constituents having been exchanged for unstable ones, the 

 safeguard of its vitality is removed, and it perishes. If, how- 

 ever, the amount of moisture in contact with a seed is. very 

 small, as in the dry earth at the bottom of a tumulus for in- 

 stance, the temperature at the same time low, and the access 

 of atmospheric air cut off, neither putrefaction nor germination 

 is likely to occur. 



When seeds are exposed to a high temperature in dryness, 

 they wUl not perish, unless the temperature rises beyond 

 any thing likely to occur under natural circumstances. 

 Edwards and Colin found that even wheat, barley, and rye, 

 inhabitants of temperate countries, would bear when dry 104° 

 for a long time without injury, although they died in three 

 days in water at 95°; and a much higher prolonged tempera- 

 ture may be expected to produce no ill effect upon seeds in- 

 habiting hotter countries. There is no apparent reason why 

 the exposure of dry seeds to the air should destroy vitality, 



