CONTRIBUTIONS FROM THE GRAY HERBARIUM OF HARVARD 

 UNIVERSITY, NEW SERIES. — No. XXX. 



A REVISION OF THE GENUS ZEXMENIA. 

 By W. W. Jones. 



Presented April 12, 1905. Received May 3, 1905. 



The genus Zexmcnia, belonging to the helianthoid Compositae and re- 

 stricted to tropical and subtropical America, was originally described by 

 La Llave and Lexarza 1 in 1824 and founded upon a single Mexican 

 species, Z. serrata. The name Zexmenia was not taken up by De 

 Candolle in his Prodromus, nor by his immediate successors in cosmo- 

 politan classification, as, for instance, Eudlicher (Gen. PI. 1838) and 

 Steudel (Nomencl. Bot. 1840). This neglect was doubtless due to the 

 fact that La Llave's plant had not been rediscovered and the type, even 

 if preserved, had not been seen by any of these authors. It is probable 

 from a reference by D. Don' 2 that La Llave sent him a specimen of his 

 Z. serrata, but even if that were the case, it was probably deposited in the 

 great Lambert Herbarium, which was sold in sections, and it would now 

 be difficult if not impossible to trace the specimen in question. 



In the Prodromus, v. 610, De Candolle described under the name 

 Lipochaeta a genus of nine species, five of which came from the Sand- 

 wich Islands and the remaining four from Mexico, La Llave's Zexmenia 

 serrata being added as doubtfully belonging to this genus. 



In 1852 Gray 3 restored the name Zexmenia, not only for its still un- 

 known type, but for Lipochaeta strigosa, DC, and several of his own new 

 species. Gray states that these are not congeneric with De Candolle's 

 Hawaiian species, to which, in his opinion, the name Lipochaeta should be 

 restricted. He also refers Lasianthaea helianthoides, DC. to Zexmenia 

 and makes it the basis of the sectional group Lasianthaea, later taken up 

 by Bentham and Hooker, f. Gray, however, did not transfer specifically 

 the five American species of Lipochaeta to Zexmenia, but this was done 



1 Nov. Veg. Desc. fasc. i. 13. 2 Trans. Linn. Soc. xvi. 170. 



3 PI. Wright, i. 113. 



