1958] 



AX ATOMY OF QUAY AN A MUTISIEAE PART II 



179 



In Guayana genera of the subtribe Gerberinae, a contrasting condition to all 

 of the above can be seen in the genus Gongylolepis (figs. 43, 44). Sclerenchyma 

 in Gongylolepis is notably absent. In the outermost bracts of G. martiana (fig. 

 44), the adaxial epidermis is sclerified and 2-4 underlying cell layers have mod- 

 erately thick walls, but no other sclerification occurs in the ground tissue of the 

 bract. Fibers are absent around vascular bundles. Cells in the abaxial half of 

 the bract have contents which suggest the laticiferous-resinous content of cells 

 elsewhere in the plant. In G. huaehamacari (fig. 43), inner bracts show no 

 sclerenchyma, and even outer bracts lack it altogether. The very fleshy texture 

 of bracts in Gongylolepis, then, is in marked contrast with the bracts of genera 

 described above. 



The other genera of Guayana Gerberinae show clear relationship to Gongy- 

 lolepis in bract structure, although they are somewhat more specialized. The 

 condition in Achnopogon (fig. 40) is virtually identical with that described for 

 Gongylolepis martianus, although the bracts are thinner. Thick-walled paren- 

 chyma cells occur beneath the sclerified inner epidermis. In inner bracts, no 

 sclerenchyma is present except in the inner epidermis. Xo fibers or true scler- 

 enchyma surround the vascular bundles. 



In Duidaea (fig. 42), precisely the same pattern is seen. As shown for P. 

 rubriceps, however, no sclerenchyma is present, only parenchyma with moder- 

 ately thick lignified walls, forming a single hypodermal layer. Such cells may 

 also be present around the vascular bundles, particularly in the basal portions 

 of the bracts. One or two layers of fibers were found to be present on the adaxial 

 face of bracts of D. iaf< i. 



Bracts of Neblinaea are not unlike those of Duidaea or Achnopogon except 

 that they contain a single layer of fibers on both faces of the bract. In addition, 

 fibers also encase the vascular bundles. Within the Guayana Gerberinae, then, 

 some differentiation along generic lines has taken place in respect to bract struc- 

 ture, although the unity of the group is evident. 



This unity is evident if comparison is made with another genus placed in 

 Gerberinae (Mutisinae of Hoffman, 1880), Nouelia. In outer bracts of N. insignis 

 (Rock 11714. A) a thick band of sclerenchyma. including the epidermis, forms 

 the inner face. The abaxial epidermis likewise is sclerified. Bundles are sheathed 

 with fibers, although additional strands consisting wholly of fibers are present. 

 Inner bracts differ only in that the adaxial epidermis alone is sclerified, the 

 fibrous bundle sheaths being as in the outer bracts. 



The genus Glossarion is anomalous in respect to bract structure, just as it is 

 in other features. The bract shown in figure 41 shows an unsclerified outer epi- 

 dermis with thick cuticle overlying 2-3 cell-lavers of thin-walled sclerenchyma, 

 which contrasts with the markedly sclerified cells on the inner face of the bract. 

 Fibers encase the vascular elements. Within the thin-walled parenchyma cells 

 of the mesophyll. there is wide variation in cell size. In lower portions of bracts 

 of Glossarion, the parenchyma is more uniform, and all cells of the bract except 

 the vascular bundles and the sclerenchyma on the inner face could be classified 

 as thick-walled parenchyma. While the bract structure of Glossarion is not un- 

 like that of several genera considered here, particularly Stenovadus, it cannot 

 be clearly referred to any of them. 



Receptacular Bracts. Only a small minority of Mutisieae possess receotacular 

 bracts. Because two genera included in this study (Stenopadus and Stomato- 



