INTRODUCTORY ESSAY. ix 
critical examination of all the forms from all countries, of those New Zealand species which are 
cosmopolitan; such operations must necessarily be left to my successors, who may receive many of 
my remarks on the dispersion of the species simply as suggestions. 
A want of materials is not, however, my only reason for withholding a decided assent to the view 
I have enunciated. There are other theories which claim more or less consideration from every un- 
prejudiced naturalist; and there are such theoretical and practical difficulties (and perhaps impos- 
sibilities) in the way of our coming to any conclusions as to the limits of the species of many genera, 
as give colour to the assumption that they have no permanently recognizable limits. A statement 
of some of these views and difficulties may be the means of throwing much light on this subject; and 
they are well worthy of the consideration of the New Zealand botanist; for islands situated far from 
continents, and in the midst of great oceans, offer many favourable points from which to start in 
such investigations. 
1. Very many naturalists consider species as permanently distinct, but demand a plurality of 
parents to account for their extensive distribution. 
2. Another large class do not consider species as permanent at all, and hold that what are called 
such, are stirpes or races (like those of man, and such of the lower animals as dogs, horses, ete.), 
subject to change or obliteration, which have been either accidentally produced, or developed accord- 
ing to some theoretical law. 
3. A third class believe in a progressive development of all organized nature, from the cell to an 
ideal type of perfection, towards which man is the last step reached. 
4. Others subscribe to various shades of these opinions, or blend them as far as they consistently 
can; some, taking even a much larger view of the limits of variability consistent with permanence of 
type than I profess to have adopted, think genera of plants permanent types, and species accidentally 
produced varieties. 
““ Arguments in favour of these views are not wanting, derived both from the animal and vegetable 
kingdoms; the chief of which are drawn from a large class of well established facts, upon the bearings 
of which the most distinguished and candid naturalists are divided in opinion: such are—the great 
number of genera whose species have baffled all attempts at circumscription by fixed characters,— 
the facility with which breeds of certain plants and animals may be propagated, and the comparative 
certainty with which some few varieties are reproduced under favourable circumstances,—the great 
facility with which many plants hybridize, and the fact of hybrids having proved fertile,—the sudden 
appearance and unexplained cause of many varieties or sports,—and the difficulty of accounting for 
the existence of plants and animals in two or more localities, between which they cannot have been 
transported by natural causes now in operation. These are all questions relating to the diffusion 
and variation of species, which will be discussed here and in the following section. 
Arguments in favour of the single creation, and permanence of species, are all based upon 
general considerations of the phenomena of distribution. Comparative anatomy, which has thrown 
such great light upon this branch of study in the sister kingdom, has not done so much for plants ; 
this arises from several causes:—1. The habits of allied plants do not differ so remarkably as those 
of animals, and there is consequently less modification of their functional organs.—2. The relation 
of these modifications to the habits and wants of the species, is in the animal kingdom directly 
appreciable, but in plants no such connection can be traced*.—3. The individual organs of support, 
* The structure of woods offers many illustrations of this; very closely allied plants (especially Zeyuminose) 
differing entirely in the nature, arrangement, and development of the vascular and cellular tissues of their trunks. 
E 
