DISTRIBUTION OF ANIMALS AND PLANTS. 673 
affect the character of the undergrowth very materially, for the 
lesser plants of a pine wood are very different from those which 
flourish beneath oaks. This would have had a very great effect upon 
_ insect life, and more or less directly influenced the number and 
character of the birds and the mammals. Even the climate would 
_ be in some small measure influenced, for a pine forest retains the 
_ Snow better than one which loses its leaves in the winter and thus 
tends to secure a more equable temperature in the region where it 
lies. 
Thus we see that an accidental drought might bring about a 
change in the assemblage of vital conditions on the surface of 
the land, as great as those which, when recorded in strata, we 
_ Accept as indicating distinct geological formations. 
It may not be amiss in passing, to call attention to the fact 
that the rate of change in land life, as far as change depends upon 
variations of temperature, must be far greater than in the sea. 
e sea knows no such frequent accidents of heat, cold and 
moisture as are at work on the land.* The difference in these 
_ Conditions is well measured by the range of migration of species. 
Our Liquidambars, Liriodendrons, and other forest trees of the 
Mississippi Valley have, during the later stages of the Tertiary 
Period, ranged as far as Greenland, or through over forty degrees 
of latitude. The greatest range of marine forms, as far as I am 
_ Ware, is not more than one-third this amount in the same limits 
‘ime. 
It is very desirable that abundant observations on the influence 
of the last winter on animal and vegetable life should be put on 
record. The author of these remarks would be glad to hear com- 
Munications on this subject. Any information of importance will 
be printed in this journal with the proper acknowledgments. 
aa lane 
. m the sea. 
: idents may produce great chang perati 
berg is readily conceived by the following example. The destruction of Cape Cod 
ela lower the average summer temperature of the region about Vineyard Sound by 
i tei orso. The result would be the expulsion from that region of at least 
i of the marine forms now found there. 
AMER. NATURALIST, VOL. VI. 43 
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