14 N. H. Agri. Experiment Station [Bulletin 284 



found that in the former an increase in hardiness is accompanied by an in- 

 crease in dye adsorption and in the latter the reverse condition obtains. 



One series of cabbage plants was grown at a temperature range of 10- 

 20° C and another series of 20 plants at a temperature range of 20-30°. 

 Sixty-two days after the experiment was set up both series of plants were 

 placed at a temperature of -5°C for 24 hours. The cabbage plants grown 

 at 10-20° showed a mortality of 30% five hours after chilling, 45% seven 

 days after chilling, and 28.2% dye remaining in solution in samples taken 

 immediately after chilling. The plants grown at 20-30° showed mortality 

 of 40% five hours after chilling, 90% seven days after chilling, and 45.0% 

 dye remaining in solution in samples taken immediately after chillmg. 



In the case of the potato two series of 25 plants each were grown at the 

 same respective temperature range as the cabbage. After the plants had 

 grown to a sufficient size they were placed at a temperature of -1.1 °C for 

 20 hours. None of the potatoes grown at the lower temperature range were 

 killed, but in the series grown at the higher range the mortality was 40 per 

 cent. The dye adsorption test showed that the plants surviving the chilling, 

 whether grown at the higher or lower temperature range, behaved in a simi- 

 lar manner, but that in the case of the non-resistant plants the series grown 

 at the temperature range 20-30° C adsorbed more dye than the plants grown 

 at 10-20°C. 



In a study of the effect of selection on hardiness, four generations of 

 Bryophyllum have been grown and chilled at a temperature -1.1 °C. The 

 effect of selection on the resistance of Bryophyllum to cold is readilv shown 

 by the fact that unselected stock showed a mortality of 85%. The first gen- 

 eration of a selection from hardy individuals showed a mortality of 27% ; 

 the second generation. 23% ; and the third generation, 35%. It would appear 

 from this that resistance to a temperature of -1.1 °C can be materially in- 

 creased by selection up to a certain point, but not beyond. 



The Jerusalem articiioke is a much hardier plant than Bryophyllum and 

 after preliminary trials a temperature of -4°C was selected as suitable for 

 separating resistant from non-resistant plants. A number of Jerusalem arti- 

 chokes were subjected to a temperature of -4°C for hours. The plants sur- 

 viving this treatment were grown to maturity. The crop obtained was saved 

 and the tubers planted in one series of pots, while tubers from unselected 

 stock were planted in another series. After the plants had grown 90 days 

 both series were exposed to -4°C for 15 hours, the results obtained being as 

 follows : plants from selected hardy stock, 40% killed ; ]:)lants from unse- 

 lected stock. IZ^/v killed. 



A study in continuation of previous work was made on the effect of low 

 and high phosphorus levels on hardiness and dye adsorption. Cabbages were 

 used in the experiment and the plants were grown in sand cultures. Phos- 

 phorus was not found to materially affect dye adsorption or hardiness. 



Fluorides have been reported as increasing the bound water in tobacco, 

 but the addition of a fluoride to sand cultures did not increase the hardiness 

 of cabbage and the dye adsorption test did not show an increase in bound 

 water. (5". Dunn — Adams Fund.) 



