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266 RELATION OF PLANT PROTOPLASM TO ENVIRONMENT. 



If attention be now turned to the spermatophytes or flowering plants, evidence 

 that has accumulated during the past quarter century entirely favors the view, 

 that many plants or plant parts are adapted to much more diverse environmental 

 relations than we formerly inclined to grant. Since the successful endurance 

 by seeds of diverse environmental changes is an important feature in the per- 

 petuation of species, we may begin our study with them. 



Quoting from the passage already referred to from Kerner he says: " Seeds 

 which are deposited on the desert sands, and survive in this position long periods 

 of drought, do certainly assume the temperature of their environment, and 

 although at noon this often amounts to 60°-70°, it does not injure these seeds: 

 since when the rainy season returns, they are roused from their summer sleep 

 and germinate in the cool and moistened soil. The highest temperature in the 

 superficial layer of soil has been observed near the equator at Chinchoxo on the 

 Loango coast. Here, in many cases it exceeds 75°, often attains 80°, and once 

 attained to even 84.6°. Nor is this soil destitute of annuals during the rainy 

 season, and without doubt the dry seeds of these plants have been lying for 

 months in the sand, sometimes heated to over 80°, without losing their germi- 

 nating power 



Of various seeds also which had been deprived of a safe amount of water, he 

 states that they can be heated for 3 hours to 100° C, and yet the greater number 

 may germinate. We can scarcely doubt that every living cell in the seeds was 

 as fully exposed to a temperature of at least 70°-75° C. as were the schizophyceous 

 algae of the hot springs. Even more remarkable were the results secured by 

 Brown and Escombe (23) , also by Thiselton Dyer (24) as to protoplasmic adapta- 

 bility of seeds to extremely low temperatures. The former experimenters selected 

 12 kinds of seed taken from eight different families, some of which were albumi- 

 nous, and some exalbuminous. The seeds were air-dried and so contained about 

 10 to 12 per cent, of natural moisture. After being slowly cooled they wer 

 immersed in a flask of liquid air, and exposed to a temperature of — 183° to — 192 

 C. for 110 hours. But on removal they showed as good germinating capacity as 



did control seeds. 



In Dyer's experiments six kinds of seeds from five families were used, and 

 their germinating capacity was tested by sets of control seeds. Some were 

 exposed in liquid hydrogen to a temperature of - 250° C. for an hour; others were 

 similarly exposed for six hours, while a third set was exposed to liquid air. A 

 germinated as perfectly as would any good seed sample, and as did the contro 



seeds. Such experiments not only confirmed the earlier results secured by 



C. de Candolle and Pictet, they strengthened Pictet's conclusion (25) that 

 "since all chemical action is annihilated at - 100° C, life must be a manifestation 

 of natural laws of the same type as gravitation." 



De Candolle's (26) added experiment of placing seeds in the snow-box of a 

 refrigerating machine at - 37° to - 53° C, for 118 days leads us to note the extreme 

 vitality of some seeds. We now have sufficient verified proof to accept it 



