354 BOTANICAL GAZETTE. [May 
grown under California conditions. On the other hand, it must 
be admitted that other factors are operating when we have to deal 
with forms whose requirements lie well within the limits of physical 
environment, or with forms widely separated in respect to the degree 
of hardiness they possess. It is difficult to conceive of any modi- 
fication of external conditions that could induce a degree of hardi- 
ness in Tonka and Stella which would even approach the hardy 
condition that obtains in Assiniboine. The fact should be kept in 
mind, however, that Assiniboine belongs to a different species from 
Stella and Tonka, and also that what is true of the apple need not 
of necessity be true of the plum or the peach. 
The investigations show a higher moisture content for tended 
apple twigs and tender peach buds than that of the hardier forms. 
In the plum; however, at least during the period of dormancy, it 
is not the relative amount of water present in the buds, but the 
relative water-retaining capacity that constitutes a distinct differ- 
ence between hardy and semihardy forms. In the apple, BEACH 
and ALLEN found that the greater moisture content of the tender 
twigs as compared with hardy twigs was much more pronounced 
during the growing season. Whether such a relation obtains 
between hardy and tender varieties of the plum during the period 
of vegetative activity has not yet been determined. It may easily 
be possible that the problem of hardiness will require specific 
investigation for each species in question, and that as yet no very 
far reaching generalizations on the subject can be made. 
In the case of the plum, microchemical studies (5) indicate 
that the dormant condition of the buds involves a protoplasmic 
change of some sort which is much more marked in the buds of the 
hardy variety. There is an evident modification in the proteins © 
of the buds, but practically nothing is known at present concerning 
the nature of this change. It is possible that there is induced as 4 
result of these modifications a very decided change in the colloidal 
condition within the cells which increases the force of imbibition, 
so that the water of the protoplast is retained against the dehy- 
drating force of freezing, and the protoplasm is not disorganized. 
There is no evidence that the hardy buds contain less moisture 
than the tender buds during the dormant period; in fact, when the 
temperature drops very low the hardy buds contain the most water 
