141 



Freezing to 220°, heat up to 122°,* vacuum, exposure through long 

 years to fluids, to alcohol, even to alcohol-sublimate, that is, to what 

 for living cells, is deadly poison — all this a desiccated seed could actually 

 endure without injury, and, according to the theory of Arrhenius, Hdmholtz, 

 or that of Lord Kelvin, could survive uninjured the flight from one planet 

 to another, t 



But how far can this desiccation proceed .without destroying the 

 germinating power ? At all events, an upper limit is fixed by the point 

 at which the seed is biunt or charred. At the degree of dryness which the 

 chemists regard as absolute, that is, after desiccation during six days at a 

 temperature of 80°, a sample of wheat still germinated fully 100 per cent, 

 but, on the other hand, it failed to endure a two days' heating at 100° 

 ( Van Tieghem and Q. Bonnier : — " Sur la vie latente des graines " ). J Similar 

 results appear im.der exposure to extreme cold, with the difference that, 

 hitherto, no degree of cold could be applied intense enough to kill the 

 dry seed. 



This resistance of the dry seeds to extremes of temperature arises from 

 the behaviour, the reaction, of the protoplasm. 



Whereas protoplasm containing water coagulates at a certain degree 

 of heat, and whereas such protoplasm is frozen to death at a certain 

 degree of cold (the degrees in question depending on the chemical compo- 

 sition of the protoplasm), this critical limit of temperature, as a result 

 of continuous slow desiccation, is very considerably raised in the 

 former case and lowered in the latter, as the classical and hitherto 

 unrefvited experiments of Chevreuil have proved. (" Deshydratation," 

 1819). De-hydrated albimiinoid substances begin to coagulate at 

 a much higher temperature than that at which hydrous albuminoids 

 coagulate. 



Chevreuil dried albumen slowly at 45°, and when it had lost 90 per 

 cent, of its water, it changed into a yellowish, hard mass ; but, on 

 water being added, it again swelled and recovered its original properties. 



In this dry state, the albumen "has 'a high power of resistance to the 

 influences of temperature, only the desiccation may not be continued 

 to a degree at which the power of absorbing water is lost and the albumen 

 can no more be restored to the colloid state. 



This is the reason why forms of living vegetables are less resistant 

 than such durable forms as seeds, spores and Sclerotia. The same applies 

 also to resistance against chemical influences. Here an unportant part is 

 played by the permeability of the seed coats. This quality of the seeds 

 involim.tarily calls to m.ind the methods employed by the Indian Joga, 

 Jogin or Fakirs,§ for the purpose of reducing the functions of the body 

 to a minimum, among which methods the most important seems to be 

 the diminution of the water-contents of the tissues. The desiccation 

 of the protoplasm also, after a certain time, reduces the change of matter 

 to the zero -point, so that in the case of seeds a change of gaseous elements 

 at least (metabolism) is no longer discernible (Becquerel^ 1. c. V. 271). 

 For the rest, however, the change of matter or gas is, in itself, no sign of 

 life, but it is a property of the organic substance under consideration — 

 a property possessed also by seeds which may be dead or even pulverized, 

 for instance, barley-seeds (Kol]cwitz\\) or pieces of a potato. In Becquerel, 

 p. 272, we find the phrase, " Pour se conserver la graine n'aurait pas 

 besoin de respirer." Seeds were kept by Cfiglioli^ in the course of his 



* Just ap. Gohn Beitr. z. Biol, der Pflanzen 1877, and Thiselton 

 Dyer and Dewar, Ann. Sc. Bot., 1901 : 599. 



I Wittmack — Landwirtschaftliche Samenkimd, 1922 : 101. 



I Bullet, de la Soc. bot. de France, 1882 : 150. 



§ N. C. Paul. . Treatise on the Joga Philosophy. Benares, 1851. 

 cit-after W. Preyer, Ueber die Erforschung des Lebens, Jena, 1872. 



II Berichte der deutsch botan. Ges, 1919 : 286. 

 Tf Nature, 1895, Oct. 3. 



