338 BOTANICAL GAZETTE [MAY 
are visible during dormancy, the metabolic processes are probably 
continued most of the time at a very greatly retarded rate. 
In the plum there is a very definite relation between dormancy 
and hardiness or the ability to withstand low temperatures without 
suffering injury. Different species and varieties manifest widely 
differing degrees of dormancy, and in general the more profound 
the dormancy, the greater is the degree of hardiness. Furthermore, 
there is a close correlation in the plum between early maturity and 
deep dormancy, because those forms which show evidence of the 
earliest maturation in autumn are likewise the ones possessing the 
greatest degree of dormancy. This is a very significant relation- 
ship, for according to CHANDLER (4) maturity is “the most impor- 
tant factor affecting the hardiness of plant tissue.” 
Dormancy in seeds has been studied quite extensively, but little 
has been done to ascertain the nature of the dormancy that occurs 
in buds. The literature extant deals largely with the possible 
effects that external factors and forcing agents may have upon the 
rest period. ScHimmpeR (10) maintains that “the protoplasm of 
the plants of temperate zones exists in two conditions, one active 
and one quiescent, and that the regular periodic alternation of 
these conditions is occasioned by inherent hereditary characters.” 
Howarp (6) asserts that “the rest sets in on account of the inhibi- 
tion of enzymic activity due to over-accumulation of the products 
of their work.” He holds that respiration and enzyme activity, 
continuing at a reduced rate, gradually remove the surplus of 
accumulated carbohydrates, and as a result the condition of dor- 
mancy is gradually lost. He further states that the fact “that 
the main dormant period happens to be coincident with the winter 
season is doubtless a mere coincidence, as the winter per se may, 
and probably does, have nothing to do with the beginning of the 
rest.” This coincidence in all probability has a deeper significance 
than that which appears in this brief statement. Dormancy, 
whatever it involves, certainly represents an accumulation of 
tendencies which have been occasioned in the experience of the 
plant by marked changes in its environmental relations. Within 
the history of the plant kingdom striking temperature changes have 
occurred, and those forms which failed in the development of a 
