1884. | Growth, its Conditions and Variations. 1219 
tage over their rivals. The nutritive superiority of exogens over 
endogens and ferns probably arises from their habit of laying up 
each year an excess stock of nutriment for employment in the 
= early periods of the succeeding year. This relieves them from 
_ the necessity of bearing their heavy covering of leaves through- 
out the storms of winter, and gives them a decided advantage in 
cold climates over evergreen plants. As for the conifers, they 
_ have reduced their leaves to needles, probably for protection 
against the destructive action of winter storms. 
We have one other matter to consider in conclusion. One of 
l the most striking phenomena of paleontological history is the 
disappearance of most of the great Herbivora and Carnivora with 
the advent of the Quaternary epoch. Such has not been the 
, case in the air and the water. The whale and the condor have 
j probably never been surpassed in size in their respective fields. 
l Significantly this disappearance on land is closely related to the 
4 coming of man. It might appear as if man, with his superior 
_ Weapons and powers, had been the moving force in this phenom- 
‘ ‘ton. Yet such can hardly have been the case. Man did not 
_ ‘ome into destructive competition for food with these larger ani- 
_ Mals, and not at all with the grass and leaf-eating tribes. He may 
t have slaughtered many, both of the Herbivora and the Carnivora, 
_ Yet he could hardly, in his early days, have greatly diminished 
4 their numbers in this manner. For the changes which took place 
_ other causes must be sought, and probably the most vigorous of 
4 these was the radical changes in climate which took place at this 
: Period. Many of the greater animals, incited perhaps by the 
_ SXistence of partly tropical conditions in the temperate regions, 
-^l made their way far to the north. On these came down the 
7 chill of the glacial epoch, whose influence must have made itself 
4 flt even throughout the tropics, and which caused a pene 
change of condition that must have been greatly destructive © 
ay life, and particularly of the bulkier and more sluggish 
After the icy period passed and genial conditions es 
Peared, the land animals were found to have markedly gree 
~ The present elephant succeeded to the gigantic ae d 
Min and mammoths as the greatest of the land anım “ x 
And with it man had fully disseminated himself over the e = 
"ew dominant form whose advent put a final. and decided chee 
_ YL xvm —yo, x11, 77 
