1957] 



ANATOMY OF GUAYANA MUTBIEAE 



447 



Stomatochaeta. 



Pollen grains of the species of Stomatochaeta agree closely with those of 

 Stenopadus other than 5". campestris. As shown for Stomatochaeta cylindrica in 

 figure 92 A-C, the grains are subprolate in shape. F.urrows are shorter than in 

 Stenopadus. The exine is psilate or nearly so, and exine thickness is approxi- 

 mately the same as in Stenopadus. Grains of Stomatochaeta, however, seem to be 

 appreciably smaller than those of most species of Stenopadus. 



Chimantaea. 



Although not conspicuously different from those of the above genera, the pol- 

 len grains of Chimantaea have somewhat more prominent spines and greater exine 

 thickness. While some species are spinulose, such as C. rupicola (fig. 93 A, B), 

 others are more nearly psilate, such as C. similis (Fig. 93 C). The variation in 

 shape of pollen grains is approximately that found in Stenopadus, ranging from 

 subprolate to prolate sphaeroidal. In size, the pollen grains of Chimantaea also 

 fall within the range found in Stenopadus. 



Quelchia. 



Pollen grains of Quelchia are easily separable from the above genera by virtue 

 of the greater exine thickness and somewhat more prominent spines. Quelchia 

 barcteata (fig. 94 A, B) is typical for the genus, as indicated by the material 

 available. As shown in table 1, exine thickness and spine length are appreciably 

 greater in Quelchia; in shape, however, the grains are subprolate to prolate 

 sphaeroidal, like those of Stenopadus. 



Stifftia. 



The genus Stifftia, although not found on the Guayana Highland, shows some 

 degree of relationship to the above genera and may be considered in this con- 

 nection. The pollen grains of Stifftia chrysantha (fig. 91 A, B) have a remarkable 

 feature not previously reported for Mutisieae. Evenly arranged on the surface of 

 these grains are eleven areas of thickened exine, three on each intercolpar face 

 and one at each pole. These thickenings are the result of greater development 

 of the outer ektexine (fig. 91 B). Numerous wide but very short spines or emer- 

 gences occur on the thickened areas of the exine as well as on the unthickened 

 areas. However, no such thickened areas are found on the pollen of Stifftia uni- 

 flora, the grains being evenly spinulose. The pollen grains of S. uniflora, not 

 illustrated here, would match closely the drawings of Chimantaea rupicola in 

 figure 93 A, B. In shape, the pollen grains of these two species of Stifftia are 

 dissimilar, since S. chrysantha has large, subprolate grains, while those of S. 

 uniflora are smaller and prolate sphaeroidal. Excepting the thickened areas in S. 

 chrysantha, the exine thickness of these two species is very similar; likewise 

 both have long, narrow furrows. 



Wunderlichia. 



Before discussing the genera which have corollas bilabiate or ligulate in form, 

 the genus Wunderlichia may be mentioned. As suggested by Wodehouse (1929 t>), 



Explanation of Figures 92-95 



FIG. 92. A-C, Stomatochaeta cylindrica; A, pollen grain; B, optical section of grain at 

 equator; C, optical section of grain at pole; D, S. condensata, optical section of grain at 

 pole. FIG. 93. A, Chimantaea rupicola, pollen grain; B, C rupicola, optical section of 

 grain at equator; C, C. similis, optical section of grain at equator. FIG. 94. Quelchia 

 bracteata; A, pollen grain; B, optical section of grain at equator. FIG. 95. Glossarion 

 rhodanthum\ A, pollen grain; B, optical section of grain at equator; c, section of inner 

 ektexine tangential to grain surface. Figure 95 C, X 1000. All others, approximately X 

 800. Specimens represented are listed in table 1. 



