408 Scientific Intelligence. 



of our predecessors should from time to time be carefully read and 

 compared together. But in the majority of cases there is no dis- 

 pute at the present day respecting the historical value, that is the 

 operative influence on posterity, of works written three hundred 

 or even one hundred years ago. 



" But it is a very different matter when the author of a book 

 like mine ventures, as I have done for sufficient reasons, but at 

 the same time with regret, to sit in judgment on the works of 

 men of research and experts, who belong to our own time, and 

 who exert a lively influence on their generation. In this case the 

 author can no longer appeal to the consentient opinion of his con- 

 temporaries; he finds them divided into parties, and involuntarily 

 belongs to a party himself. But it is a still more weighty con- 

 sideration that he may subsequently change his own point of view, 

 and may arrive at a more profound insight into the value of the 

 works which he has criticised ; continued study and maturer 

 years may teach him that he overestimated some things fifteen or 

 twenty years ago, and perhaps undervalued others, and facts, 

 once assumed to be well established, may now be acknowledged 

 to be incorrect. 



" Thus it has happened in my own case also in some but not in 

 many instances, in which I have had to express an opinion respect- 

 ing the character of works which appeared after 1860, and which 

 to some extent influenced my judgment on the years immediately 

 preceding them. But this was from fifteen to eighteen years ago 

 when \ was working at my History. It might perhaps be ex- 

 pected that I should remove all such expressions of opinion from 

 the work before it is translated. In some few cases, in which this 

 could be effected by simply drawing the pen through a few lines, 

 I have so done; but it appeared to me that to alter with anxious 

 care every sentence which I should put into a different form at 

 the present day would serve no good purpose, for I came to the 

 conclusion that my book itself may be regarded as a historical 

 fact, and that the kindly and indulgent reader may even be glad 

 to know what one, who has lived wholly in the science and taken 

 an interest in everything in it old and new, thought from fifteen 

 to eighteen years ago of the then reigning theories, representing 

 as be did the view of the majority of his fellow botanists. 



"However these remarks relate only to two famous writers on 

 the subjects with which this History is concerned. If the work 

 had been brought to a close with the year 1850 instead of 1800 

 I should have hardly found it necessary to give them so promi- 

 nent a position in it. Their names are Charles Darwin and Karl 

 Nageli. I would desire that whoever reads what I have written 

 on Charles Darwin in the present work should consider that it 

 contains a large infusion of youthful enthusiasm still remaining 

 from the year J 859 when the Origin of Species delivered us from 

 the unlucky dogma of constancy. 



"Darwin's later writings have not inspired me with the like 

 feeling. So it has been with regard to Nageli. He, like Hugo 



