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ANATOMY OF GUAYANA MUTISIEAE PART II 



173 



of the midvein sheath extension (see figs. 25, 26). Fibers are abundantly present 

 around the midvein in this genus, although lacking in the lateral veins; lateral 

 veins are, however, jacketed by cells like those of the midvein sheath extension. 

 The three species of Duidaea may be very easily separated on the basis of hypo- 

 dermal sclerenchyma. Duidaea tatei (fig. 25) has a prominent adaxial hypo- 

 dermis, composed of sclereids, which extends around the margins, where it is 

 broader. Duidaea phi if alia (fig. 26), on the contrary, is entirely lacking in such 

 sclereids. Duidaea rubriceps (fig. 27) possesses a hypodermis a single layer thick 

 (except at the margins, where it is two cells in thickness) which completely 

 encircles the leaf. 



The leaf of Glossarion (fig. 23) combines features of many of the taxa de- 

 scribed above, although it cannot be referred to any particular genus. A thick 

 cuticle is present on both upper and lower epidermis. A hypodermis, consisting 

 of a single layer of small isodiametric sclereids, occurs on the adaxial face. One 

 feature not seen in any of the other genera is the elongate shape of the thin- 

 walled sclereids composing the adaxial half of bundle sheath extensions. The 

 lower half of the sheath extension consists of isodiametric thin-walled scleren- 

 chmya, which also forms sheaths on smaller veins not possessing extensions. No 

 hypodermis is present adjacent to the lower epidermis; numerous uniseriate 

 hairs, not shown in the portion illustrated, characteristically occur on the lower 

 epidermis. 



In summary, excellent generic distinctions are present among most of the 

 genera, such as Stomatochat ta, Chimantaea, Duidaea, and Glossarion. The leaves 

 of Stenopadus could be distinguished from those of Gongylolepis by means of 

 the presence of laticiferous cells in the latter. The leaves of Stenopadus, in 

 addition, tend to be much thicker than those of Gongylolepis. Quelchia leaves 

 resemble those of both Stenopadus and Gongylolepis, although they are closer 

 to the latter in possession of bundle sheath extensions (absent from Stenopaelus 

 except for S. cucullatus) and laticiferous cells. Leaves of Achnopogon and 

 Xeblinaea are within the range of variation found in Gongylolepis. 



The complex structure of leaves in Guayana Mutisieae, their abundant scler- 

 enchyma or thick-walled parenchyma, massive cuticles, and possession of bundle 

 sheath extensions are features usually associated with plants of habitats dry 

 during at least part of a year. The leaf structure of such species as Chimantaea 

 mirabilis is what one would expect to find in a rather xeric environment, in fact. 

 One notable feature which is found in most of the genera is a development to 

 some extent of a hypodermis, a structure which occurs (together with sheath 

 extension) in such a distant mutisioid as Nouelia. The absence of hypodermis in 

 such genera as Stifftia and Hesperomannia (Carlquist 1957c) does indicate that 

 although it is a widespread phenomenon in the tribe, it is not a universal one. 



Although investigations of leaf anatomy of other mutisioids are apparently 

 lacking, comparisons can be made with other Compositae. Hypodermis has been 

 reported in species of Celmisia (Astereae) and in Senecio munroi by Solereder 

 (1908), and in Veronia luschnathiana by Grimm (1904). Bundle sheath exten- 

 sions are apparently not infrequent in the family, as is indicated by reports of 

 their occurrence in various species by Betts (1920), Shields (1951) and Carl- 

 quist (1957d). In none of the genera studied by these authors, however, does 



