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XXVI. On certain Species of Carduud and Cnicus which appear 

 to he dioecious. By Thomas Smith, Esq. F.R.S. and L.S. 



Read February 5, 1822. 



Although Linneus founded his orders in the class Syngenesia 

 upon nice distinctions, drawn from the various modes in which 

 the florets of different sexes are arranged in each capitulum, the 

 fact that many species were dioecious, or had the male and female 

 flowers on distinct plants, almost entirely escaped his observa- 

 tion ; for in the last edition of his Genera Plant arum, published 

 in 1764, he remarks, that Gnaphalium dioicum is a rare example 

 of the separation of the sexes in this class. 



Jussieu in his Genera Plantarum, published in 1789, does not 

 appear to have been aware of any other example than the above, 

 for he observes at the end of his generic character of Gnapha- 

 lium, " Species una dioica insigni exceptione." 



It has however been pointed out to me by my friend Mr. Brown, 

 that at the time this observation of Jussieu's was published, Frie- 

 drick Ehrhart had shown that some species of Tussilago were 

 dioecious : and our native species Tussilago hybrida and Peta- 

 sites now rank as one only under the name of Petasites, which 

 is the male, hybrida being the female*. Mr. 



* Vide Friednck Ehrhart Beit rage zur Natwkunde, vol. iii. 1788. The paper is 

 however dated December 1783, and had previously been printed (I believe) in the 

 Hanover Magazine, probably about the latter date. 



It may be proper nevertheless to note, that M. Cassini, whose extended and accurate 

 investigation of this class gives great weight to his opinion, has come to an opposite 



conclusion 



