16 



PJnjdolcxjical Pre-determluatioii 



Treatment of the seeds sub- 

 sequent to the 6 hours soak- 

 ing in water, but previous 

 to sowing* 



Strength of 

 acid used 



1 % solution of 

 boric acid 



1 % 

 1% 

 1% 



Period of 

 soaking 



1 hour 



2 hours 



3 „ 



„ 



Table XL 



Results noted in the plants after about 



5 weeks' growth 



Plants poor, with small 

 yellowish leaves 



Plants poor, with small 



yellowish leaves 

 A very few plants came up 



and these were very feeble 

 Few very feeble etiolated 



plants produced, leaves 



very small and few in 



number 



7 weeks' growth 



Growth of plants moderately 

 vigorous, but their leaves 

 remained yellowish and 

 were much smaller than 

 those of the controls 



Crowtli very poor although 

 showing a decided im- 

 provement 



* The seeds were placed on damp sand for a few days at a favourable temperature and 

 were then sown in garden soil. Only those treated for the shortest period {i.e. 1 hour) had 

 germinated after an interval of 3 days. 



Similar experiments carried out with wheat gave results analogous to 

 those obtained with haricot beans. 



The present authors, working with Brassica alba, have shown that 

 concentrations of carbonic aciddO) and boric acid (41) which rapidly kill 

 the growing root, have no injurious effect upon any part of the embryo 

 in the ungerminated but fully swollen seed. We may distinguish three 

 ranges of increasing concentration of these two acids, as follows. (1) A 

 range of low concentration in which the seeds germinate, but suffer injury 

 after germination. (2) A range of intermediate concentration in which 

 the germination of the seeds is inhibited. No injury to any part of the 

 embryo or seedling can be observed even after prolonged treatment 

 with this concentration of acid when the seeds are finally brought to 

 germination in an acid-free medium. In this region marked injury is 

 shown, however, by seeds which are allowed to germinate before being 

 placed in the acid medium. (3) A range of higher concentration in 

 which the seeds suffer injury whether ungerminated or germinated. 

 The concentration of acid used by Morel lies in this third region which 

 causes injury to the ungerminated seed. 



This difference between the effect of chemical solutions u])on the 

 growing plant and their effect upon the seed before germination is not 

 confined to acids but appears to be general. For instance, Hicks{i3:ina ii), 

 who tested the effect upon seeds of a number of chemical fertilisers, 



