IQ2I] 



PACK—JUNIPERUS 



55 



a normal length, while at o± i° C. there was a slow but definite 

 growth. It is important to note that 15 C. seedlings developed 

 first and appeared the most healthy and sturdy. These seedlings 



TABLE XXI 



Effect of light and temperature on rate and extent of growth* 



♦Average of so trials. 



at i5°C. also showed the earliest and greatest development 

 chlorophyll. Light did not seem to affect unusually the extent or 

 rate of growth. 



Pigments. — Carbohydrates and temperature may condition 

 chlorophyll development. The seedling was found to develop 

 chlorophyll in total darkness. Thus the cotyledons become green 

 long before they break out of the coat. Chlorophyll appeared 

 first in the cotyledons and accompanied the formation of starch. 

 This points to the conclusion that soluble carbohydrates are neces- 

 sary for the formation of chlorophyll, the view advanced by 

 Palladin (28). Table XXII gives the results of experiments 

 planned to determine the effect of light and temperature on green- 

 ing. This shows that light affects in no way the rate or apparent 

 depth of greening. It also shows that at 30 C. and at o±i° C. 

 chlorophyll did not develop. As the plastids were found to be in 

 good condition, it was thought probable that a lack of building 

 material was inhibiting chlorophyll development. Glucose cultures 

 were made, therefore, but the seedlings again failed to develop 

 chlorophyll. This indicates that a certain temperature is necessary 

 for chlorophyll development, regardless of carbohydrate supply, 



