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in part so many apparent discrepancies in hardiness in different 
individuals of the same species, and, furthermore, it accounts for 
different results in different winters. So much depends upon the 
amount of water present in the plant; the kind of growth it made 
the season before, whether vigorous or slight, early or late; 
whether or not it was pruned, and if so, how much, and when; 
whether or not it was exposed to drying winds or direct rays of 
the sun; whether or not it had been recently planted or moved, 
and so, how well it had become established in’ the soil—these are 
some of the things we may mention briefly to show how the 
physiological condition of individuals may vary. In addition, we 
should note that there is in all probability an inherent predis- 
positional factor (residing in the protoplasm itself )—ji.c. pre- 
disposing a given individual to injury from cold. This of course 
is bound up with the constitution of the protoplasm. If such 
predisposition exists in animals and ourselves (and there seems 
to be no doubt of this) it seems reasonable to assume that it occurs 
also in plants. The following paragraph deals with this concep- 
tion from a genetic point of view. 
Flereditary Nature of Hardiness 
In an earher number of this journal, Dr. Orland Ik. White, form- 
erly Curator of Plant Breeding at the Garden, has stated that 
since hardiness in plants is an hereditary character, “its basis is 
or heredi- 
”Y 
dependent on the presence or absence of certain genes 
tary units in the nucleus of the plant cell. Since new genes (and 
thus new characters) may arise by mutation, it is conceivable, he 
says, that a given plant species may have among the individuals 
composing it some ‘hardy’ mutants. In other words, cold re- 
sistant varieties may perhaps arise within a plant species by mu- 
tation.! 
Reasons for Discrepancies in Data on Hardiness 
Because of these individual differences; and because of the 
complexity of the factors whose interaction determines the de- 
gree of a plant’s susceptibility to winter injury, any collection 
1 White, O. E. Geographical distribution and the cold-resisting character 
of certain herbaceous perennial and woody plant groups. BrooKLyNn Bor. 
Garp, Recorp 15: 1-10. 1926. 
