496 BIOGRAPHICAL SKETCHES. 



had visited him at Upsala, and he kept up a correspondence 

 with him to the end of the venerable botanist's life. He caught 

 from Fries, or he developed independently, and cultivated to 

 perfection, that sense of the value of the indefinable something 

 which botanists inadequately express by the term " habit," 

 which often enables the systematist to divine much further than 

 he can perceive in the tracing of relationships. Upon this, in 

 direct reference to Fries, and with a use of the term that seems 

 to correlate it with "insight," Tuckerman remarks : "So great 

 is the value of Habit in minds fully qualified to apprehend and 

 appreciate its subtleties, that such minds may not only antici- 

 pate what the microscope is to reveal, but help us to under- 

 stand its revelations." It should be remembered, however, 

 that when Fries did the best of his work there were no micro- 

 scopes of much account ; and it is probable that Tuckerman 

 would have done more, and perhaps have reached some differ- 

 ent conclusions, if he had earlier and more largely used the 

 best instrumental appliances of the time. One advantage, how- 

 ever, of his way of study, and his philosophical conception of 

 an ideal connection of forms which are capable of a wide play 

 of variation, was that he took broad views of genera and spe- 

 cies. So he was quite unlike that numerous race of special- 

 ists who, in place of characterizing species, describe specimens, 

 and to whom " genus " means the lowest recognizable group 

 of species. 



As to the vexed question in Lichenology, which came to 

 him rather late and seemed to threaten the stability of his 

 work, it was most natural that, at his time of life, he did not 

 take kindly to the Algo-f ungal notion of Lichens, and that he 

 was convinced of its falsity by questionable evidence. 



Professor Tuckerman was much more than an excellent spe- 

 cialist. Happily, he did not become such until he had laid a 

 good foundation, for the time, in general systematic botany ; 

 and his early studies show that he was a man of scholarly cul- 

 ture over an unusually wide range. He was at home in the 

 leading modern languages ; he wrote Latin with reasonable 

 facility, and botanical Latin remarkably well ; he had given 

 serious attention to law, divinity, philosophy, and history ; and 



