30 II. WHAT IS A SPECIES? 



of varied circumstances; — (secondly) if they have flowers, 

 fertilising easily among themselves, and producing seeds 

 most usually fertile ; — (thirdly) being aff"ected by tempe- 

 rature and other external agents in a similar or nearly 

 similar manner ; — {fourthly) in short, resembling as plants 

 of analogous structure, known certainly to have descended 

 from a common stock for many generations." 



It is truly much easier to find objections against this 

 and other definitions of the term species, than to invent a 

 better. That which meets the views of one botanist, may 

 ill suit the ideas of another. Such discrepancies seem 

 to be inevitable ; arising, as doubtless they do, from the 

 natural dissimilarities which are so usually to be detected 

 between the intellectual characters of different writers. 

 Some men are more prone to abstract reasoning ; others 

 are more fitted for physical observation. Among bota- 

 nists there is a large preponderance of the simple ob- 

 servers over the sound reasoners ; far more of them 

 merely observe and compare visible facts ; far fewer of 

 them are competent to deduce correct inferences from 

 observed facts. 



It is needful to point attention to these mental dif- 

 ferences between botanists ; because not a few of them 

 evidently imagine that they derive some right or qualifi- 

 cation to pronounce dogmatic opinions in matters of 

 ratiocination, on the ground of being good technical de- 

 scribers or good systematic classifiers. Whereas, it often 

 happens, that the peculiar mental bias which adapts them 

 to shine in either of the latter departments, is precisely 

 one which disqualifies them for correct reasoning. So 

 frequently is this the case, that we might hold it a rule, 

 to which the exceptions are very few, that a good techni- 

 cal botanist is a shallow reasoner. 



Perhaps no definition of the term species can be framed, 



