GERMINATION OF SEEDS. 597 



complete dehydration, the injury was less, and the slower 

 the ascent, the less the harm. At 110° C. the injury was 

 more pronounced; half an hour at 122° C. 'killed' 99 per 

 cent, of corns of Hordeum, whereas those of Avena with- 

 stood exposure of three hours. The fatality was always 

 increased with the duration of exposure. Above 122° C. 

 all seed were ' killed '. 



It is curious that resistance to high temperatures is so 

 modified by the aqueous content of seeds, as these and 

 other experiments show, while that to low ones is un- 

 affected, as De Candolle and Pictet have shown. 



In Just's paper, results obtained by Haberlandt are 

 quoted which show that desiccated seeds resist exposure 

 of forty-eic^ht hours at 100^ C. ; these results were confirmed 

 by Krassan. 



The results of van Tieghem (16) on this subject con- 

 tradict those of almost all other observers ; it was found 

 that if fruits of cereals were dried at 100° C. till no further 

 loss of weight ensued, ' vitality ' was completely destroyed. 

 The contradiction is difficult to explain ; that the seeds 

 were not completely dehydrated seems certain, for it is 

 known that certain carbohydrates can be reduced to con- 

 stant weight at 100^ C, and yet yield more water without 

 decomposition at higher temperatures. 



It will not perhaps seem out of place to emphasise once 

 more the undoubted fact, that one cannot speak of a 

 constant specific, or even individual, resistance to en- 

 vironment ; variation in origin and treatment affects the 

 ' vitality ' of seeds correspondingly. 



Goff found that seeds of Triticiun (^vu/gare f) and Zea 

 Mays could be germinated six and five times respectively, 

 when the periods of germination were separated by in- 

 tervals of desiccation for seven days. Van Eyck,^ who 

 quotes this, obtained like results ; seeds that had germinated 

 were removed every twenty-hours and submitted to dehydra- 

 tion in an exsiccator for a week : these operations were re- 

 peated till the power was lost. The accompanying table 

 gives his results : — 



^ De la germination repetee des graines, Atm. Agron., 21, 1895, 236. 



