VOLUME LXxI NUMBER 5 
Las 
DOtANIGA = Gsaehl Th 
MAY £0921 
DORMANCY AND HARDINESS IN THE PLUM 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 280 
P. D. STRAUSBAUGH 
(WITH FOUR FIGURES) 
It is a well known fact that the trees of our latitude develop 
buds during the period of vegetative activity, which remain 
inactive or dormant throughout the succeeding period of climatic 
conditions unfavorable for growth and development (AsKENASY 1). 
Although these dormant structures have been recognized for a 
long time, practically nothing is known concerning the factors 
involved in their development or the internal conditions that obtain 
during the time of their relative inactivity, Growth and develop- 
ment take place normally up to a certain point and then suddenly 
cease, in some instances several weeks earlier than the occurrence 
of temperatures sufficiently low to arrest growth activity. In late 
Winter, the rest period is broken in many species, and growth 
changes are manifested long before the incipiency of warmer 
weather. Up to the present no specific experiments have dealt 
with the nature of the forces that induce cessation of growth in 
these bud structures, or the changes involved, either internal or 
external, in the resumption of the activity after a certain period of 
rest. The term “rest” as used here refers to a condition of greatly 
reduced, or possibly (for very short periods under certain conditions) 
a complete arrest of growth activity. Although no growth effects 
337 
