Feb. 1902.] BOTANICAL SOCIETY OF EDI^'BUEGH 189 



To elicit that manifestation of irritability which we 

 call growth, and which we take as evidence of life in the 

 seed, three tonic stimuli are necessary. Not only must 

 these be applied simultaneously, but they must be applied 

 in the proper intensity. If any one or all the combination 

 be applied in too great intensity, life may be destroyed. 

 On the other hand, there is reason to believe that a single 

 stimulus may be separately applied at an intensity far in 

 excess of the limits, and yet produce no fatal result. In 

 the experiments of Brown and Escombe (loc. cit.) seeds were 

 subjected for 110 hours to the temperature of liquid air — 

 183° to — 192°C., and in those of Thiselton-Dyer, were im- 

 mersed for six hours in liquid hydrogen — 250°— 252° C, 

 and yet germinated. Jencic ("(Ester. Bot. Zeit.," li., 1901, 

 p. 268), again, found that when air-dried seeds were sub- 

 jected to a temperature of — 18°C., their germination was 

 accelerated. 



The latitude in regard to trespass of the upper cardinal 

 point of temperature appears to be more limited. Dixon 

 (" Nature," Ixiv., 190 1, p. 256), however, finds that of seeds, 

 specially Mcdicago sativa, eyi^o^e^ for an hour to 110°C., 

 and a further hour to 121° C, 10 per cent, germinate. 

 Jodin ("Compt. Eend.," 129 (1899), p. 893) states when 

 seeds of peas and cress are heated at 60° C. for twenty-four 

 hours, and then for ten hours at 98° C, 30—60 per cent, 

 retain their germinative power; further, these seeds in sealed 

 tubes containing some water-absorbent, such as quicklime, 

 will germinate after being submitted for twenty days to a 

 temperature of 40° C. If we seek in the animal kingdom 

 for cases to parallel the resting seed in its condition of 

 " vie latente," or scheintod, we find them, perhaps, in the 

 desiccated state of tardigrada and rotifera, and very likely 

 it will be found that these organisms, when thoroughly 

 desiccated, can withstand the same extraordinary tests as 

 the dry seed. 



As to the molecular condition of the living matter of 

 the dry seed, little can be said. De Candolle compares it 

 with that of an explosive mixture : so long as the necessary 

 conditions are unapplied the mixture remains quiescent, 

 and will so remain for an indefinite period. Brown and 

 Escombe are of De Candolle's opinion, and hold that the 



