GLACIAL PHENOMENA IN MAINE. 100 
ample opportunity for studying the ripening 
process. In attempting to determine the cause 
of these changes, it ought not to be forgotten 
that they occur locally, and also make their 
appearance on particular trees much earlier 
than upon others; so early, indeed, as to show 
clearly the fallacy of the prevalent idea that 
they are caused by frost. The temperature 
remains ten or fifteen degrees above the freez¬ 
ing-point for a month and more after a good 
many of our trees have assumed their bright 
autumnal hues. The process is, no doubt, 
akin to that of ripening in fruits; especially 
in such fleshy fruits as turn from green to 
yellow, purple, or red, like apples, peaches, 
plums, cherries, and others. The change in 
color coincides with changes in the constitu¬ 
tive chemical elements of the plant; and this 
comparison between the ripening of foliage 
and fruit seems the more natural, when we 
remember that fruits are but a modification of 
leaves, assuming higher functions and special 
adaptations in the flower, so as to produce 
what we call a fruit. The ripening process by 
which the leaves take on their final colors is as 
constant and special as in the fruits. The cher- 
