THE STEM AND THE LEAF 61 
per year continues to increase, and then diminishes. For ex- 
ample, the long-leaf pine (fig. 229) grows only about 3 $ inch 
the first year. For the first fifty years it makes an sense 
annual growth of 14 or 15 inches; for the next fifty years, 4 or 
5 inches; and from one hundred years to extreme old age, 
about 14 inches. It usually lives about two hundred years. 
Fie. 41. An isolated white oak tree destroyed by a violent windstorm 
Photograph by Paul Sargent 
The growth of the younger portions of most plants is quite 
unequal, as may be learned from the study of a rapidly growing 
stem, such as the morning-glory.! It will also prove interesting 
to measure such plants as corn, broom corn, hemp, and pole 
beans, to determine whether they elongate more by day or 
by night, and during warm or during cool weather. 
1¥For an illustration of this unequal growth, see Bergen and Davis, 
Practical Botany, p. 17. Ginn and Company, Boston. 
