lii'i'i.] Failure of Black Yeo Oats in Glamorgan. 4G7 



The figures are interesting from several points of view. Tn 

 the first place they show that differential tests conducted under 

 conditions less favourable to germination and growth than 

 ordinary conditions are competent to reveal defects in a sample 

 I hat might be overlooked if only the ordinary test was conducted ; 

 and in any event to bring out such defects more prominently. 

 Thus with double watering the behaviour of Radnorshire Sprig, 

 relative to Culberson is even more marked than under normal 

 watering.* 



It will be seen that the effect of half watering has been but 

 slight on the healthy control sample, but that quarter and 

 double watering have had a very appreciable influence on the 

 percentage of finally established plants — quarter watering in 

 particular having shown a striking decrease in respect of energy 

 of establishment. 



In view of the complete failure of Black Yeo under the 

 droughty conditions prevailing during the season of 1921 it is 

 of particular interest to find that whereas Radnorshire Sprig 

 was adversely affected to the greatest extent by double watering, 

 the Black Y T eo was affected to the greatest extent by quarter 

 watering. The energy of establishment of Black Yeo under 

 quarter watering was almost negligible and actually less than 

 that of Radnorshire Sprig, although Black Yeo showed a " nor- 

 mal condition " germination of 97 per cent, and Radnorshire 

 Sprig but 23 per cent. 



It is thus evident that the seeds of Black Yeo were not normal, 

 and although attaining to a high percentage of germination 

 were defective in some physiological respect which rendered 

 them particularly and exceptionally susceptible to the influence 

 of drought. This showed itself also in the poor energy of ger- 

 mination and of establishment under normal conditions It 

 should be added that the growth habit of the established Black 

 Yeo plants confirmed that this is a Winter Oat.t 



The growth of established plants did not differ appreciably 

 either between the three samples or between the differential 

 waterings, except that those subjected to quarter watering were 



° These results are in keeping with those previously recorded by 

 Stapledon (Seed Studies : Red Clover, with special reference to the County of 

 Origin of the Seed, Jour. Ayr. Sd., X. (1), Jan., 1920), who found that tests 

 conducted with Red Clover at temperatures above the optimum brought out 

 defects of the seed in a very striking manner. 



f That this circumstance as such was without influence on the complete 

 failure in Glamorgan is suggested by the fact that black winter oats sown in 

 the spring in the trials at Aberystwyth established themselves normally and 

 produced relatively good crops. 



F 2 



