168 Physiological P re-determination 



The "Potentiality" op the Seed as influenced by the 

 Weather Conditions at the Time of Harvesting. 



Nothing of a definite nature from the point of view of physiological 

 pre-determination can he stated in this connection as there are no 

 critical observations available. The general effect of dry climatic con- 

 ditions during the maturation and harvesting of the seed crop will be 

 to hasten maturity. Districts which have been found most valuable 

 for industrial seed-production are those in which uninterrupted dry 

 weather conditions prevail during late summer and far into the autumn. 

 Wet weather conditions during maturation and at the time of harvest- 

 ing will obviously not only affect the degree of maturity of the seed, 

 but will also be unfavourable for gathering and storing the crop. 



It has been shown repeatedly {e.g. Duvel(7); Dorph-Petersen (5)) that 

 the deterioration of seeds during storage runs parallel to the percentage 

 of moisture in the air-dry seed. A slight difference in the amount of 

 water present in the air-dry seed at the time of storing causes marked 

 differences in its subsequent germination capacity, the lower water- 

 content being in the majority of cases the best. 



Duvel'slT) conclusion is that the deterioration of seeds in dry storage 

 is due to oxidations (cf. also Babcock(2); Becquerel(3), and others). The 

 amount of COg produced by seeds stored air-dry can be correlated with 

 their percentage moisture-content and with the loss of vitality sub- 

 sequently observed. 



Conclusions. 



A consideration of the results reviewed above makes it clear that 

 the question as to whether differences in the resulting plant are pre- 

 determined by the use of seeds differing in degree of ripeness cannot be 

 regarded as satisfactorily answered in the case of any single species. 



This is due to the fact that all the recorded comparisons between 

 plants grown from immature seeds and plants grown from mature seeds 

 appear to have been complicated by some period of storage. Immature 

 seeds are less tolerant of storage in the dry condition than mature seed, 

 so that in the case of the comparisons which have been made, the total 

 yields from immature seeds are usually less than those from mature 

 seeds owing to the fact that a smaller percentage of the immature seeds 

 germinate. 



When in such experiments comparisons are made between yield per 

 plant, however, the difference in favour of the plants from mature seeds 



