22 NOTES OX SOME TASMANIAN EUCALYPTS, 



collecting grounds for the private and public museums of 

 Europe, in some cases the types have been lost. Even 

 where they are available, the material is often of the 

 scantiest description, and in such cases we have sometimes 

 had to adopt a convention that such and such a tree, whose 

 identity has been definitely ascertained, shall be looked 

 upon as the type. It is in the search for types, in the en- 

 deavour to place the nomenclature of species upon a settled 

 foundation, that the botanist, with the limitations of the 

 material available to him, has often made mistakes, which 

 would in many cases have been impossible had adequate 

 material been available. All branches of natural history 

 afford similar illustrations of tentative efforts made with 

 imperfect material. 



In this connection it may be well to be reminded of the 

 pronouncement of the immortal Plooker : ('') 



"I need hardly ren^Trk, that the very different opinions 

 "entertained by botanists as to what amount and constancy of 

 "difference between many forms of plants should constitute a 

 "species, renders all such comparisons vague; and I may add 

 "that no two or more botanists c-an ascertain the comparative 

 "value of their opinions except they have exactly the same 

 "materials to work with. It is too often forgotten that in the 

 "sciences of observation what are called negative facts and 

 "evidence are worthless as compared with positive." 



As to whether a certain plant is deemed to be a species 

 or a variety is not of the greatest importance. Those who 

 look upon a certain plant as a distinct entity have it in 

 common that they are agreed that it is distinct, and this 

 is really important; those who look upon one as a variety 

 of another go further, and indicate affinity ; this may be a 

 valuable opinion. 



It is to be borne in mind that a changed environment 

 induces moiiDhological changes in a plant. Thus when E. 

 regnaiia grows in grassy bottoms, its trunk is mainly 

 smooth, but as it creeps up the hill-sides its height of rougli 

 bark extends up the trunk. Of course species-fonnation 

 is going on every day, and eventually plants may vary 

 sufficiently from, say, the regnans type for one to say they 

 have ai-rived at the stage when they are specifically differ- 

 ent. 



The position seems to be something like this : — 



1. Taxonomy is the science of the systematic arrange- 

 ment of plants based on moi-phological characters. 



2. There is no evidence that we may have two plants, 

 precisely similar in morphological characters, which are 

 not specifically identical. 



(C) Hooker's Introd. Flora of Tas., XXX. 



