821 



Akt. CLXXXV. — On the Varieties of Betula alba of Linneeus, de- 

 scribed as distinct Species by some authors.* By Hewett C. 

 Watson, Esq., F.L.S. 



There is, perhaps, in the present day, scarcely any circumstance 

 more calculated to impede the progress of botanical science, and 

 to throw difficulties in the path of the younger botanist, than the 

 growing fondness for changing names, and for inventing species in 

 books which have really no distinct existence in natm'e. I believe 

 that it would be no exaggeration of the number of these spurious spe- 

 cies now enumerated in the descriptive Floras of Britain, if I were to 

 estimate them at about two hundred. But in the present paper my 

 remarks will be restricted to those imaginary species which have been 

 carved out of our common birch, the Betula alba of Linnaeus. 



When the last volume of Smith's ' English Flora ' was published, 

 in the year 1828, this tree was described as a single species under the 

 name of Betula alba. But the author of that still valuable work did 

 slightly mention a pendulous variety, which had been published in 

 Germany, as a distinct species, under the name of Betula pendula. 

 And in the various editions of the ' British Flora,' we find the autho- 

 rity of Sir W. J. Hooker added to that of Sir J. E. Smith ; since the 

 latter work still describes the birch-ti*ee as one species only, though 

 stating, in the last edition (1842), that the name of B. glutinosa 

 appeared in the ' Edinburgh Catalogue,' as if belonging to a distinct 

 species. 



In Lindley's ' Synopsis of the British Flora,' which followed shortly 

 upon the completion of the ' English Flora,' we find the pendulous 

 form described as a distinct species, under the name of Betula pen- 

 dula. Both. 



In the second edition of the Catalogue published by the Botanical 

 Society of Edinburgh, in 1841, the views of Dr. Lindley are not re- 

 cognized ; his species, Betula pendula, being enumerated only as a 

 variety of B. alba. To compensate this reduction of one pretended 

 species from the number, another was found, and introduced into the 

 Catalogue under the name of B. glutinosa, Wallr. 



In that capital work, the recently published ' Manual of British 

 Botany,' by Mr. C. C. Babington, Dr. Lindley's B. pendula is at last 

 utterly cashiered, being not even given as a variety. But to make up 



* Read before the Botanical Society of London, November 3, 1843 ; communicated 

 1)V the author. 



