1958] 



ANATOMY OF Gt'AYAXA MUTISIEAE — PART II 



177 



parenchyma gradually, so that cells with walls of intermediate thickness may 

 be found beneath the abaxial selerenchynia. Xo nests of sclereids. however, are 

 present in the mesophyll of bracts, although bundles are very prominently 

 encased by fibers. In outer bracts, xyleni and phloem of bundles are frequently 

 separated by such fibers. 



The bracts of Chimantaea (figs. 34. 36) are distinctive in having more abun- 

 dant sclerenchyma development than any of the preceding". This sclerenchyma. 

 however, is not disposed as in Stenopadus or Stomatochaeta. since neither fibrous 

 bundle sheaths nor nests of sclereids are present. Instead, the entire bract, both 

 inner and outer, is converted into sclerenchyma except for a small band (in 

 outer bracts, fig. 34) or occasional pockets (in inner bracts, fig. 36) of thin- 

 walled parenchyma on which the vascular bundles are located. In their extremely 

 woody structure, these bracts surpass those of other genera in this study. 



Involucral bracts of Quelchia (fig:. 39). although they are thinner, have a 

 combination of characters which does not match those of the above genera. The 

 adaxial epidermis, and parts of one layer beneath it. are sclerified. as is the 

 abaxial epidermis, but the remainder of the bract is thin-walled parenchyma. 

 No fibrous bundle sheaths are present. The outer bracts have the structure shown 

 for an inner bract of Q. cardonae in figure 30 except that the abaxial epidermis 

 is unsclerified. 



Comparisons with other Gochnatinae seem pertinent here, both for demon- 

 strating the relative similarity of bract structure, despite certain differences, in 

 the four above genera, and for showing the diversity to be found in putatively 

 closely-related members of this tribe. The only other mutisioid for which infor- 

 mation on bract structure is available is Hesperomannia (Carlqnist 1057c). so 

 that two other genera, which are probably not distantly related to Guayana 

 Gochnatinae. are described here. Stifftia ( fig. 32) is notably different in that 

 its bracts, although they have a texture like that of Chimantaea bracts, have an 

 entirely different development of sclerenchyma. The adaxial epidermis may be 

 sclerified. All other sclerenchyma in the bract, however, is in the form of dis- 

 crete fiber bundles, and no isodiametric sclereids are present in the mesophyll. 

 Some of these fiber bundles contain vascular components, although vascular 

 tissue in bracts of Stilftia is at a minimum. Where xylem is present, it occurs 

 in the centt r of one of these fiber strands, with the phloem at the outside of the 

 strand separated from it by numerous fibers. 



The involucral bracts of Wunderlichia tfig. 33) are notable in that a promi- 

 nent band of sclerenchyma covers the inner face with the exception of the epi- 

 dermis. In this respect it resembles the bract of Stenovadus connellii shown in 

 figure 30. In contrast to 8. connellii. however, no sclerenchyma of any kind is 

 associated with the vascular bundles. Groups of parenchyma cells may develop 

 into mesophyll sclereids which are much larger and more thin-walled than those 

 of the adaxial sclerenchyma. 



A quite different pattern is illustrated by the involucral bracts of Hcspero- 

 mannia ( Carlqnist 1057c). In this genus, no sclerenchymatous sheath is present 

 on bundles. A thin band of sclerenchyma is present on the inner face of the 

 bract including the epidermis, and there is a rather prominent development of 

 fibers toward the outer face. The latter sclerenchyma may be outside of or 

 intercalated between the bundles. A similar pattern occurs in Anastraphia 

 coweUii (Howard 5098, GH) with the exception that in addition to the isolated 



