22 Pinisiological P re-determination 



These results should be accepted with considerable reserve since the 

 pot-culture experiments were conducted with relatively few plants and 

 the probable errors of the experiments were not determined. 



A rejiular increase in yield with increased strength of the solution 

 employed was reported by J. Craig (7) as the result of soaking- pea seeds 

 for one hour in solutions of NaNOg of the following concentrations, viz. 

 1 oz., 2 oz. and 3 oz. of the salt to one gallon of water. 



One more instance may be noted. An increase in the tillering of 

 several varieties of wheat to the extent of 12-8 per cent, and 20-6 per 

 cent, respectively as the result of treating the seed with (NH4)2S04 (3 per 

 cent, solution) and NH4NO3 (3 per cent, solution) was recorded by Wild 

 (42) in the Agricultural Journal of New Zealand, 1914. In order to estimate 

 the tillering 20 plants were taken at random from the various experi- 

 mental plots, and in the case of each variety tested it was found that the 

 effect of the treatment upon the tillering of the plants was a positive 

 one. But here again the experimental data upon which the conclusions 

 were based appear to be totally inadequate. 



(Ill) Hydrogen peroxide. 



Several workers have recorded observations on the effect of hydrogen 

 peroxide treatments of seeds upon germination and upon the seedlings 

 produced from the treated seeds. It would appear that in some cases 

 hydrogen peroxide in certain concentrations may stimulate germination 

 (cf. Pinoy and Magrou(28)), but the usual effect recorded is a retardation 

 of the germination of the seeds. 



Massee(22) when testing the effect of hydrogen peroxide upon seeds 

 with a view to its possible utilisation in seed-sterilisation found that 

 although germination was retarded, the growth of the seedlings eventually 

 produced was rapid so that in many cases at the end of three weeks the 

 plants from the treated seeds were distinctly larger than those from 

 untreated seeds used as controls. But unfortunately the records of 

 investigations with hydrogen peroxide are usually completely unsatis- 

 factory for the reason that the strength of the solufioii employed is not 

 determined. 



CONCLrsioXS. 



In concluding this review of the literature bearing upon what we 

 have termed physiological pre-deterniination we may briefly summarise 

 the available evidence. The evidence, as a whole, seems to show that 



