1957] 



ANATOMY OF GUAYANA MUTISIEAE 



473 



follow the bands of stigmatoid tissue to the base of the achene, uniting with the 

 ovule trace (fig. 116 I). A single vascular strand results from the union of all of 

 the bundles at the achene base. The ovule trace is simple. 



DISCUSSION 



The floral vascular patterns given above serve as additional taxonomic criteria 

 in separating the genera of Guayana Mutisieae investigated in the present study. 

 The segregation of Stomatochaeta and Chimantaea from Stenopadus is justified by 

 the differences found in floral venation among these genera. Quelchia is distinct 

 from these genera in certain details, though similar in most respects. Within the 

 Gerberinae studied in this paper, simplification from the patterns seen in Nebli- 

 naea and Gongylolepis bracteata is seen in other species of Gongylolepis, such 

 as G. fruticosa, Duidaea, and Achnopogon. This is in accord with the suggestion 

 of Maguire (1956; and Maguire & Wurdack 1957) that these latter taxa are advanced 

 derivations from a gongylolepoid stock. The anamalous corolla form of the genus 

 Glossarion is clarified by study of the underlying venation pattern. As stated by 

 Maguire and Wurdack (1957), this ligulate corolla form seems to be a modification 

 of a basically actinomorphic form. 



The differences in floral venation described above are significant in that they 

 suggest evolutionary trends within the Mutisieae. As indicated by Maguire (1956), 

 the genera of Guayana Mutisieae considered here represent not only a geographical 

 assemblage of genera, but also a series of primitive forms in the two subtribes 

 concerned, Gochnatinae and Gerberinae. Since the Gochnatinae are generally 

 considered to contain the most primitive features to be found in the Mutisieae as 

 a whole, the characters of Guayana Gochnatinae become of interest in attempting 

 to deduce primitive structural features in Compositae at large. The introduction of 

 Stifftia, a member of Gochnatinae occurring outside the limits of Guayana, into 

 this study was intended to demonstrate the most primitive floral venation pattern 

 which could be found in non-Guayana Gochnatinae. 



It seems apparent that the vascular characters described above cannot be 

 arranged in a single line from complex to simple. In such species as Stenopadus 

 kunhardtii and Gongylolepis pedunculata, it seems probable that increase in 

 number of vascular bundles from the basic condition has taken place. However, 

 the following possible sequences in the evolution of the Mutisioid flower may be 

 suggested: 



(1) Corolla. Median veins in corolla-lobes of Mutisieae have been regarded as 

 primitive in the genus Anastraphia (currently treated as Gochnatia) by Koch 

 (1930a); a similar interpretation was given from Hesperomannia (Carlquist 1957a). 

 The progressive loss of median bundles may be regarded as an indication of 

 advance. It may be that the close relation between stamen traces and lateral 

 bundles provides an explanation for the discarding of median, rather than lateral 

 bundles in the vascular simplification of the composite flower. It seems likely 

 that separate pairs of laterals in the corolla-tube have preceded united lateral 

 bundles. In some Stenopadus species considered here such adjacent lateral 

 bundles were often not united even in their downward extension into the achene. 



Explanation of Figure 116 



FIG. 116. Glossarion rhodanthum (Maguire, Wurdack & Bunting 37190), portions of 

 flowers drawn to show venation. A, corolla; B, C, upper portions of corollas of other 

 flowers; D, style; E, achene; F-I, sections of corolla base and achene at levels indi- 

 cated. A-D, x 4.5; E-I, x 9. 



