376 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[yol. 9, No. 3 



there are 32 remarkably clear-cut, distinct Guayanan species. They, by virtue 

 of general facies and morphological characterization, fall into several readily 

 recognizable natural generic groupings. Of these, the largest and basic as- 

 semblage (Stenopadus with fifteen . clear-cut species) displays most strongly 

 those characters which are generally accepted as primitive in the Compositae, 

 viz., massive, many-flowered terminal, usually solitary, homogamous, rayless 

 heads subtended by numerous multi-serial, relatively large phyllaries; strongly 

 paleaceous receptacles; carnose, regular corollas with complex morphology and 

 vascular supply; complex achenial and stylar vasculation; simple stigmatic 

 branches; subpaleaceous pappus; ample veiny leaves; and arboreous habit, in 

 which the trunk may reach a diameter of several decimeters, and in which the 

 wood is compact, very hard and heavy, with a specific gravity as much as 1.1 

 or 1.2. 



The remaining gochnatinioid genera (Chimantaea, Stomatochaeta, and Quel- 

 chia) (the extra-Guayanan Stifftia excepted), considered to have been derived 

 from Stenopadus or stenopadan stock, display in common besides specialized 

 differentiation along their own generic lines, thin-textured corollas with simpli- 

 fied morphology and vascularization. These more simple corollas are considered 

 to be derived or "advanced." Characterization believed to be of phyletic 

 significance is given for the several genera in question. 



Stenopadus. 



Significant trends or lines of modification have taken place within Stenopadus 

 which have led to sectional differentiation. The four sections show complete 

 or partial geographic containment. The section Kunhardtia, of four species, is 

 considered basic or the most primitive because of its large, mostly many- 

 flowered, numerously bracted heads, strongly paleaceous receptacles, and 

 corollas with stamens attached within the corolla at the union of the distinct 

 tube and limb. The single species of the section Campestris has similar but 

 urceolate corolla with merely flexuous lobes. In the four species of the section 

 Connellii, the attachment of anther filaments has moved up to the sinus, the 

 receptacular pales have been reduced to a few in number or are lacking, and 

 the pappus setae are filiform. In the six species of the section Stenopadus, 

 the filaments are attached in the sinus, the receptacles femain strongly paleace- 

 ous, and leaves are strongly reticulate-veined. This last distinguishing feature 

 makes members of the section Stenopadus immediately and easily recognized. 



Stifftia 



Morphologically most closely associated with Stenopadus, but geographically 

 and pfobably historically most distantly set off from it. Further remarks are to 

 be addressed to these problems. 



Stomatochaeta 



Consists of a compact closely interrelated group of four species distinctly 

 set off from Stenopadus by fruticose habit, thickly coriaceous leaves with 

 reduced nervature, small few flowered heads, with one or few receptacular 

 pales, "advanced" corollas with simple vasculature, stiffly erect lobes much 

 exceeding in length the undifferentiated 10-nerved tube, and very short, blunt 

 style-branches. 



Chimantaea. (to be described in a succeeding paper; Mem. N. Y. Bot. Gard. 

 9:000). 



This is perhaps the most remarkable presumptive derivative of Stenopadus. 

 As in Stomatochaeta, the leaves are thickly coriaceous, the receptacle epalea- 



