108 Canadian Record of Science. 
a specific temperature, to which it is specially adapted. 
The seeds of wheat and barley will not germinate below 
41° F., while they grow more rapidly at 83.6° F., and cease 
all further growth beyond 108.5° F. Corn will not ger- 
minate below 48° F. ; its vegetation becomes most vigorous 
at 92.6° F., but ceases when the temperature exceeds 115° F. 
The squash seed demands at least 56.6° F., attains its best 
growth at 92.6° F., and beyond a superior limit of 115° F. 
its existence ceases. We thus find that the total range cf 
temperature, between the superior and inferior limits, 
under which the life of wheat and barley can be accom- 
plished, is 67.5° F. For corn, 67° F. and for the squash 
58.4° F. From these simple facts, which might readily be 
extended to other species, we learn that each plant not only 
requires a certain degree of heat for the completion of its 
normal functions—a degree which varies with the species or 
with the type—but that the extremes of temperature which 
a plant can successfully withstand, may be much greater in 
some cases than in others. And also that when all the 
energies of the organism are dormant, it is in that condition 
best adapted to its resisting these extremes, especially of 
low temperature. ‘Thus in our own locality, trees which, 
in the month of August, flourish under a mean temperature 
of 67.5° F., sometimes subjected to a maximum of 91°, still 
exist without apparent injury, when in January or Feb- 
ruary, they encounter a mean 6.8° F., and a possible 
minimum of 26° below zero, thus giving an extreme range 
of 117° F. Weare aware, however, that as we approach 
the equator, the extremes are greatly reduced and the 
general conditions under which vegetation flourishes, become 
much more uniform. 
From this we perceive that when the conditions of envi- 
ronment are of an unusual character, the organism must be 
affected in one or more of its functions, with a constant ten- 
dency towards permanency of variation according to the 
strength and duration of the modifying influences. It is 
true that the conditions to which any organism may be sub- 
jected—as in transfering a plant from an equatorial to a north 
