THE CONDITIONS FOR THE DISTRIBUTION OF PLANTS. 99 
‘The more important of these causes are—the conditions for the 
distribution of plants and the means of distribution. (Besides 
these, a very important item is the comparative power of plants of 
holding their own in the struggle for existence, a subject which 
still requires the most careful study, and which I am not prepared to 
deal with here.) The conditions for distribution of plants are 
chiefly these, viz., the climate, the adaptation of plants for climatic 
influences, the natural quality of the soil, and thenecessity of fertilisa- 
tion for plants. You are all. aware of the very distinct features of 
vegetation, as represented in different regions, countries, or even 
localities of the same province. You will have noticed that the 
vegetation of the seashore is very different from that represented 
further inland; that the plants of our hills are to a great extent 
of other species than those occurring in the plains, or that almost 
every different locality has its peculiar flora. When we ask for 
the reason of this, the reply will often be found in the various 
natural conditions of the said locality, but what I especially wish 
to point out to you is, that a little closer observation of the plants 
themselves will prove that peculiarities in their structure or 
apparently casual appendages make them particularly adapted for 
the natural conditions presented by the locality, and that they are 
of the utmost importance with-regard to distribution of the plants. 
Bor the observation of this fact, as for so many important discoveries 
‘n regard to natural objects, we are specially indebted to your great 
Countryman, Charles Darwin, who pointed out the way, which has 
been followed by several botanists, among whom I may mention 
Dr. Hermann Miiller (Lippstadt), Dr. Friedrich Hildebrand 
(Leipsic), Dr. A. Kerner (Vienna), and Professor Otto Kunze 
(Leipsic), as authorities for many of the views expressed in my 
paper. The field is, however, so vast, that the subject will probably 
never be thoroughly exhausted. It is particularly interesting, not 
only in affording ample evidence in support of the much disputed 
theories of Darwin, but also in explaining the necessity of almost 
very organ of plant life. Of the natural conditions for distribu- 
tion of plants none is more decisive than the climate. The local 
range of temperature is in many instances an absolute necessity for 
the growth of plants, and by this circumstance the limits of dis- 
tribution for every species of plants are generally fixed. As to the 
exact range of temperature necessary for the individual species, the 
requirements greatly differ, but it may be regarded as certain, that 
