96 
IOWA ACADEMY OF SCIENCES. 
NOTES ON FOREST DISTRIBUTION IN IOWA. 
BY T. H. MACBRIDE. 
The peculiar character of our American forest geography 
early attracted the attention of intelligent observers. Civilized 
men, Frenchmen, crossicg the continent from the Atlantic 
seaboard, after threading for two hundred leagues a forest 
almost unbroken, suddenly found themselves in the presence of 
vast treeless plains, extending westward across a large portion 
of the central Mississippi valley. In wonder and admiration 
the voyageuT looked upon these great plains, grass-grown and 
flower- bedecked, and found them counterpart to the green 
meadows of France; to them he gave the name prairie, a word 
now so familiar as to have long lost for all Euglish- speaking 
men every vestige of foreign origin. How these great mead- 
ows ever came to exist or persist in the region where they 
first were seen, or why the forests of the east should so sud- 
denly stop was a problem the voyageur could not solve, and has 
been a problem from the days of the voyageur until now. 
In these times of almost universal forest extermination, 
when w'e are in sight of the era in which Americans must 
laboriously undertake the work of re-forestration, it is well that 
we should closely attend to conditions once established by 
nature, that we may hereafter act with her assistance, for in 
plant distribution, whatever our blunders may be or have been, 
nature we may be sure has seldom made a mistake. 
In general, two factors are said to control forest distribution 
on the planet; the one, rainfall, the other, temperature. If the 
rainfall is deficient there can be no forest, rainfall seems never 
to be excessive, and if a region is too cold there is no forest. 
In proof of this we have but to look at the high altitudes and 
latitudes of the earth. What makes our Iowa problem there- 
fore peculiar, is the fact that forest distribution here, as else- 
where in prairie regions, does not accord with these general 
