PRESIDENTIAL ADDRESSES. oe 
and flora of stony hills. The hydrophytic societies occur in and near our water- 
courses, ponds, sloughs, marshes, and springs. The mesophytic societies are con- 
fined to the border-land between the hydrophytes and xerophytes, and more 
especially in the shade of the lowland woods. The halophytes are found in the 
salt marshes which occur through the interior of the state. 
Although, while the conditions remain unchanged, the societies remain in an 
equilibrium, there is, nevertheless, what might be termed a conflict of societies 
going on everywhere. As soon as the conditions change, even slightly, one so- 
ciety will gain an advantage over its neighbors. There seems to be little doubt 
that the forest societies are gradually encroaching on the plains. It must not be 
inferred that every species is found where are conditions best suited for its de- 
velopment. It is, rather, that each species is found where it can best compete 
with others able to endure the same conditions. For example, in Kansas the red 
cedar is found on barren limestone cliffs, and presents a gnarled and more or less 
stunted aspect. Yet, under favorable conditions—that is, ordinary rich soil—it 
produces a vigorous and symmetrical body. The same is true of the bald cypress 
of our Southern states. It is found native in swamps, and usually is flat topped 
and stunted in its growth, with a much less vigorous aspect than specimens cul- 
tivated in moderately dry soil. It would appear that they have been unable to 
compete in those localities where they could thrive best, but have been forced to 
take refuge in the stony hills, in the one case, and the swamps in the other, 
where they can maintain themselves against their competitors. So we see that 
there is a constant struggle between individuals in a society, and between socie- 
ties in a given area or region. 
Ecology also includes the wider class of distribution ordinarily called the 
geographical distribution of plants; that is, the distribution of plants on the 
earth’s surface into zones, regions, and areas. The division into zones is based 
on climatic conditions. There are four zones: tropical, temperate, arctic, and 
mountain. The regions are subdivisions of these zones of sufficient extent to 
eliminate the effect of local conditions. As examples, may be mentioned the 
great plains and the Arizona-Mexico desert region of North America, the 
steppes of Russia, and the pampas of South America. This study includes not 
only the actual distribution of plants upon the _earth’s surface, but also the 
causes which lead up to it, in so far as they are concerned with adaptation. 
Thus, we have the difficult problem of the origin and relations of the flora of a 
particular region. The conditions have not always been as they are now; but, 
under the influence of those mighty forces which have fashioned our continents, 
islands, mountains, and lakes, an indefinite number of changes have taken place 
in the relations and composition of the plant societies. Vast forests once flour- 
ished where is now a wide expanse of prairie. Palms inhabited the polar circle 
and arctic plants were spread broadcast over the temperate regions. Floral areas 
have had their rise and fall. First one species is dominant, then another. You 
are all familiar with the distribution of our arctic plants: how, in preglacial 
times, a more or less tropical flora surrounded the pole; how the oncoming cold 
drove all vegetation southward; how a modified vegetation followed the retreat- 
ing glaciers, but left arctic representatives stranded on the high mountain 
tops of the whole northern hemisphere; how Greenland is so remarkably poor 
in species compared with other lands in the same latitude, because most 
of its flora was driven southward into the ocean; how the flora of eastern United 
States resembles more closely that of Japan and eastern Asia than it does that 
of California, because a similar flora found similar conditions in these two 
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