r92t] PACK—JUNIPERUS 55 
a normal length, while at o+1°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* 
LENGTH OF HYPOCOTYL IN MM. FROM TIME OF TRANSFER 
TEMPERATURE| LicHT 
3 days 7 days 11 days 13 days 18 days 26 days 
30° C Dark I 5 7 12 18 20 
Se Dark 10 35 40 55 60 Seedling 
oes Dark 4 18 29 Seedling cpaslenens ens 
rw Dark 3 10 30 35 Seay A Se 
to € Light 3 II 29 30 Seedling |......... 
5° Dar 2.5 4 12 15 26 35 
Oo °C Dark ° ‘ I 2 3 4 5 
regen ae Dark ° Killed ° ° ° ° 
*Average of 50 trials. 
at 15°C. also showed the earliest and greatest development of 
chlorophyll. Light did not seem to affect unusually the extent or 
rate of growth. 
PicMENTS.—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#1°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, 
