214 NEW ZEALAND PLANTS. 
‘* evolution.” 
That evolution is a reality no biologist doubts, though 
regarding its methods there is great disagreement and no absolute 
certainty, but quite the contrary. Many theories have been put 
forth, but three stand out prominently. The first, of which Darwin 
and Wallace are the illustrious authors, is known as the theory of 
Natural Selection. It takes the well-known fact that all organisms 
vary in all directions, and considers that if certain variations, are 
beneficial they will persist, and by degrees, in the course of an 
enormous number of generations, become so intensified that a new 
species will result. As for the unbeneficial varieties, they will in 
course of time perish through the conflict with the more fitted. 
This theory is firmly believed in by many; especially has it a great 
following amongst zoologists. 
In 1901 the eminent Dutch botanist Professor Hugo de Vries 
put forward his Mutation theory. He showed by numerous far- 
reaching experiments extending over many years that certain 
varieties, differing markedly from the parent in some hereditary 
characteristics, appear all of a sudden, and that a new species 
comes at once into the world without the lapse of long years. 
If such a species is adapted to its surroundings it will remain ; 
but, if not, it will go to the wall. These de Vriesian species are, 
of course, not the aggregate species of floras, but the little species 
mentioned in Chapter XI—the true entities of the plant-world. 
A third school, largely botanical, believes that the direct action of 
the conditions to which a plant or animal is exposed evokes changes 
in accord with such conditions. This is called the New Lamarckian 
theory, or the doctrine of the inheritence of acquired characters. 
For instance, if a plant grows in a wind-swept locality, according to 
this view, in the course of time its descendants might have the form 
of wind-swept plants no matter where they grew. Or if a land- 
plant could be grown successtully in water, it might develop special 
structures peculiar to water-plants, and these in time would become 
hereditary. The behaviour of many New Zealand plants could 
easily be brought forward in support of this theory. 
Then, a year or two ago, another Dutch botanist, Dr. Lotsy, read 
a paper before the Linnean Society of London supporting his belief 
that virtually all species had arisen through hybridism. Although few 
would go to so great a length, it-seems fairly certain that species do 
at times arise in that manner, and that the so-called “ variability ”” 
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