FLORA OF SCOTTISH LAKES 
157 
From the first dawn of modern science until almost the middle 
of the last century, the chief aim of those who interested themselves 
in vegetation, beyond the ornamental, useful, or medicinal properties 
of plants, was in the accumulation of dried specimens into herbaria, 
in the grouping of the plants into families so as to exhibit as nearly 
as possible their natural relationships, in giving names to the various 
species, and in appending to each a curt diagnosis of a few prominent 
external features in a language that could be understood only by the 
initiated ; the great desiderata of botanists being, to have a vast 
number of species in their collections, and to be constantly adding 
still more. To a certain extent these studies were useful, but it was 
most unfortunate for the cause of science that such desires and 
methods should have dominated the fields of botany so long. With 
the advent, however, of such master-minds of science as Charles 
Darwin, Herbert Spencer, Hermann Mliller, Julius Sachs, the Hookers, 
and many others a new era arose, and then botanists began to con- 
sider plants under the refulgent rays of the new light which these men 
had kindled : the real studv of nature then began. Instead of the 
ultima Thule of botanists being the addition of one more plant to their 
lists, men began to thirst for a knowledge of the phenomena of plant 
life and its causation — for, in fact, a Philosophical Botany. In his 
Principles of Biology^ Herbert Spencer gave the keystone to the arch 
when he wrote therein : — " Everywhere structures in great measure 
determine functions ; and everywhere functions are incessantly modi- 
fying structures. In nature, the two are inseparable co-operators ; 
and science can give no true interpretation of nature, without keeping 
their co-operation constantly in view."' 
The first plant life that occurred upon the earth was probably of 
aquatic habit, and water has ever continued the very soul of vegetable 
existence, without which its life is impossible. 
When the ancestors of our present terrestrial phanerogamic flora 
began their phylogenetic development from aquatic forms of plant 
life, their first need must have been an efficient water- transporting 
system. As the new forms began to extend into places more remote 
from watery environments, so the need for rapidly carrying water 
through the plant-body would increase. Those forms unable to re- 
spond to this requirement would die out, and their places would be 
occupied by others more fitting. After enormous epochs of time, 
during which the struggle of adaptation has proceeded apace, it comes 
about that at the present day the terrestrial plants that dominate the 
surface of the earth are chiefly those that have best succeeded in pro- 
viding themselves with an efficient water-transporting system. With 
phanerogams of aquatic habit there is no necessity for the elaborate 
development of this arrangement. When, therefore, a normal ter- 
