Longevity of Seeds. 183 



or under water beinpf gerrainable, from the classical case of 

 Mumni}'- Wheat downwards. Here and there a long-lived seed 

 has accident alh'' been hit upon, but in the great majority of cases 

 the records are incorrect. 



The Conditions for Longevity. 



These are partly inherent in the seed itself, and partly due to 

 the external conditions. As regards the latter, all observations 

 agree that fairly cool, dry, airy conditions preserve seeds best, 

 while in the soil seeds last longer in the deeper layers than in the 

 surface one^s. Seeds with impermeable coats are less dependent 

 on the external conditions than ordinary'- ones, and may resist 

 immersal in poisons or poisonous gases for years when dry and 

 unswollen. Such seeds are naturally also most likely to last 

 longest in the soil. 



According to Fischer, however, the seeds of Sagittarid and 

 similar plants may be kept under water for several years without 

 losing the power of germination, and although the contents of 

 the seed are moist. This is a far more remarkable fact than the 

 long duration of certain seeds when drv', because in the former 

 case there is a greater tendency to chemical change, and feeble 

 respiration probably takes place. ^ 



A few seeds (Willows, etc.), are killed by air drying, and 

 according to Poissotf seeds of Cacao begin to die 36 hours after 

 drv'ing outside the fruit. In the case of all ordinary seeds, the 

 drier the seeds the longer iXioj are likely to last, and this applies 

 more especially to starchy seeds. 



The chief factor in longevity is the inherent character of the 

 seed itself. In 1894'* I showed that seeds capable of withstand- 

 ing thorough drying assume a perfectly dormant condition in 

 which they do not respire and are not living, although tliey have 

 a power of restoring life potential in them for a longer or shorter 

 period of years. Similar conclusions were made by de Candolle, 

 who appears to have considered that all seeds, if carefully dried 

 and preserved, would retain an indefinitely prolonged power of 



1 Crocker (I.e.) has thrown considerable doubt on the correctness of Fischer's views. 

 •2 Bulletin de la Soc. bot. de France, 1903, t. 1., p. 337. 



3 Ewait, Trans. Liverpool Biol. Soc, 1894, vol. viii., p. 234. 



4 De Candolle, Arohiv. d. Sci. phys. et nat : see also Nature, 1893, p. 34S. 



