14-4 PROCEEDINGS OP THE AMERICAN ACADEMY. 



later by C. H. Schultz. 1 In 1858 Mueller 2 collated briefly nine species 

 of Zexmenia, not including those previously referred to Lipochaeta. 



At the time of Bentham and Hooker's Genera Plantarum Zexmenia 

 had been extended to include about twenty-five species, and was divided 

 into three sections : Wedelioides, Lipochaeta, and Lasianthaea, In the 

 present treatment the achenial characters alone have been made the basis 

 of the sectional division, and it has seemed undesirable to maintain Lipo- 

 chaeta and Lasianthaea as sections of the genus, for their species are 

 often so nearly alike habitally that it is difficult to distinguish them, 

 and in respect to the achenial characters these two sections form a very 

 homogeneous group, which may be very fitly regarded as Zexmenia proper 

 as by Hoffmann 3 (Euzexmenia). In this portion of the genus the achenes 

 are all strongly angled, triangular in the ray-flowers, and much flattened 

 (except in Z. Salvinii) in the disk-flowers. True wings (developing 

 after anthesis) are never present, but the angles are often produced into 

 wing-like longitudinally striate margins. The awns are generally longer 

 in the disk-achenes than in the ray-achenes. In the former they 

 frequently exceed the length of the body of the achene, although they 

 are sometimes quite short. On the ray-achenes they are sometimes re- 

 duced to short stoutish teeth. When the intermediate pappus scales (squa- 

 mellae) are developed to the length of 1 mm. they are always united to 

 form a small cup or short tube at the summit of the achene. The entire 

 pappus is continuous with the margins of the achene, there being no con- 

 striction or pappus-disk at the summit, as will be found in Auchenocarpa, 

 to be described later. The inflorescence is of a terminal cymose 

 character, but often appears umbellate or fasciculate by a shortening of 

 the internodes. In a few species peduncles arise from several of the 

 upper nodes. This section includes about twenty-five species. 



The § Wedelioides, proposed by Bentham and Hooker, f. 4 was used by 

 its authors to iuclude an obvious mixture of plants not very nearly re- 

 lated. The name was probably suggested by the Wedelia-like habit of 

 such species as Z. reticulata, Z. caracasana, and Z. helianthoides, Benth. 

 & Hook, f., which can no longer be referred to Zexmenia. Wedelioides 

 as a section of Zexmenia would, therefore, better be abandoned. The 

 portion of the § Wedelioides, Benth. & Hook, f., which it seems best to 

 retain in Zexmenia, together with several more recently described species, 



i Sch. Bip. in Seem. Bot. Voy. Herald, 305-306. 



2 Mueller in Walp. Ann. v. 225-226. 



s Hoffm. in Engl. & Prantl. Nat. Pflanzenf. iv. Ab. 5, 238. 



* Gen. ii. 373 (1873). 



