INTRODUCTORY ESSAY. 1.x 



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, etc.), 

 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 consecruently 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 Leg* 

 differing entirely in the nature, arrangement, and development of the vascular and cellular tissues of their trunks. 



c 



