INTRODUCTORY ESSAY. 



on this subject upon a very extensive examination of living plants in all latitudes, with my attention 

 particularly directed to the influence of external causes, not only on the general phenomena of 

 tion, but also upon individuals. Added to this, I have paid a great deal of attention to variable 

 plants, both of tropical and temperate climates, and studied them in a living state, both wild and cul- 

 tivated, and also in the herbarium. The result of my observations is, that differences of habit, co- 

 lour, hairiness, and outline of leaves, and minute characters drawn from other organs than those of 

 reproduction, are generally fallacious as specific marks, being attributable to external causes, and easily 

 obliterated under cultivation. It has hence been my plan to group the individuals of a genus which 

 I assume after careful examination to contain many species whose limits I cannot define, that the 

 species shall have the same relative value as those have of allied genera whose specific characters are 

 evident. I doing so I believe I have followed the practice of every systematist of large experience 

 and acknowledged judgment since the days of Linnreus, as Bentham, Brown, the De Candolles, 

 Decaisne, Asa Gray, Jussieu, Lindley, and the Richards ; names which include not only the most 

 learned systematists, but the most profound anatomists and physiologists. I am far from supposing 

 that the same materials of a difficult group would receive precisely similar treatment at the hands of 

 each of these eminent men ; but their results would so closely approximate as to be in harmony with 

 each other, and available for scientific purposes : with all, the tendency would be to regard dubious 

 species as varieties, to take enlarged views of the range and variation of species, and to weigh 

 characters not only per se, but with reference to those which prevail in the Order to which the species 

 under consideration belong. 



In working up incomplete floras especially, I believe it to be of the utmost importance to adopt 

 such a course, and to resist steadily the temptation to multiply names, for it is practically very diffi- 

 cult to expunge a species founded on an error of judgment or observation*. There is further an in- 

 herent tendency in every one occupied with specialities to exaggerate the value of his materials and 

 labours, whence it happens, that botanists engaged exclusively upon local floras are at issue with those 

 of more extended experience, the 'former considering as species what the latter call varieties, and 

 what the latter suspect to be an introduced plant the former are prone to consider a native. There is 

 much to be said on both sides of such questions : the local botanist looks closer, perceives sooner, 

 and often appreciates better, inconspicuous organs and characters, which are overlooked or too 

 hastily dismissed by the botanist occupied with those higher branches of the science, which demand 

 a wider range of observation and broader views of specialities ; and there is no doubt but that the 

 truth can only be arrived at through then- joint labours; for a good observer is one thing, and the 

 knowledge and experience required to make use of facts for purposes of generalization, another : 

 minute differences however, when long dwelt upon, become magnified and assume undue value, and 

 the general botanist must always receive with distrust the conclusions deduced from a few species 

 of a large genus, or from a few specimens of a widely distributed plant. 



I have been led to dwell at length upon this point, because I feel sure the New Zealand student 

 will at first find it difficult to agree with me in many cases, as for instance on so protean a Fern as 

 Lomaria procera, whose varieties (to an inexperienced eye) are more dissimilar than are other species 

 of the same genus. In this (and in many similar cases) he must bear in mind that I have examined 



* The state of the British flora proves not only this, but further, that oue such error leads to many more of 

 the like kind : students are led to over-estimate inconstant characters, to take a narrow view of the importance and 

 end of botany, and to throw away time upon profitless discussions about the difference between infinitely variable 

 forms of plants, of whose identity really learned botanists have no doubt whatever. 



