the Vitality of Seeds by an Electrical Method. 



83 



surface B (giving therefore current of injury of positive direction) 

 gives blaze currents in the negative direction in response to an induc- 

 tion shock in the positive direction (= an equivocal blaze in the 

 polarisation direction) and to an induction shock in the negative direc- 

 tion (= an unequivocal blaze in the homodrome direction). If the 

 bean is horizontally sliced at the upper surface A instead of at the 

 lower surface B, the current of injury is negative and the blaze 

 currents positive in response to both directions of excitation. 



3. A boiled bean gives no blaze currents in either direction but only 

 small polarisation counter-currents, in the positive direction after a 

 negative current and in the negative direction after a positive 

 current. 



The next obvious point to be tested is the effect of anaesthetics 

 upon the response. The results depend upon strength of excitation 

 employed, and duration of ansesthetisation. Cceteris paribus, the strong- 

 effect of a strong stimulus is far more refractory to the action of an 

 anaesthetic than the smaller effect of a weaker stimulus, and in the 

 former case the suppression is apt to be incomplete, or when complete 

 to be definitive. To obtain temporary suppression it is necessary to 

 choose a sufficient but not too strong exciting current, and to anaesthe- 

 tise by ether rather than by chloroform. 



In a preceding paragraph it has been mentioned that a fresh vigorous 

 seed gives a large blaze current, whereas a stale or moribund seed gives 

 little or no response. The next step was obviously to compare similar 

 seeds submitted to various enfeebling modifications, as well as different 

 crops of similar seeds, the electrical tests being controlled by parallel 

 germination tests. 



The first and most readily effected comparison is that between the 

 reactions of fresh seeds and of the same seeds killed by boiling. The 

 result of this comparison is unmistakable and invariable. Fresh seeds, 

 giving unequivocal blaze currents with an E.M.F. of - 01 to 0*10 volt, 

 give no blaze currents whatever after they have been boiled, but only 

 polarisation counter-current with an E.M.F. of 0'0005 to 0'0020 volt. 

 The seeds upon which I have made this test have been leguminous 

 seeds, such as shelled beans and peas boiled in water, and the kernels 

 of stoned fruits such as cherries, plums, and peaches boiled in their 

 protected state.* 



* The reaction is abolished at a temperature considerably below that of boiling 

 water ; e.g., at a temperature of between 40° and 50° of a warm moist chamber. 

 Miss S. C. M. Sowton has carefully investigated this point and that relating to the 

 effect of anaesthetics, by aid of photographic records, which are in fact indispens- 

 able in connection with these two points. It is also abolished by congelation 

 (at — 3 d to — 5°), which causes a sudden large electromotive effect at this point. 

 On recovery of normal temperature no blaze can be obtained, and on recongelation 

 there is no electromotive effect at the critical temperature. 



