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ANATOMY OF GUAYANA MUTISIEAE 



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the drawings of entire achenes. In these sections, the outlines of the corolla 

 and nectary (or style base) are shown, and for the achene, those of the achene 

 wall and ovule. The two strands of stigmatic tissue, which occur as fused bands 

 in the style, separating to lateral positions on the inner face of the achene wall 

 (rejoining at the base of the achene cavity and running toward the micropyle) 

 are shown as variously shaped ellipses in these drawings. 



The terms "vascularization" and "venation" in this study refer only to 

 xylem elements, unless phloem is specifically mentioned. In many bundles, the 

 phloem is coincident with the xylem. It should be understood, however, that this 

 is by no means always the case. In achenes particularly, strands of phloem may 

 be present without any accompanying xylem. Such strands may be found as in- 

 ternal bundles in the achene. In addition, they interconnect bundles in the achene 

 top. In species in which the xylem of stamen traces was not seen to connect 

 with other bundles at the base of stamen traces, phloem elements could often 

 be seen to interconnect these bundles. In all species, strands of phloem, con- 

 necting to bundles at the achene top, branch to form an anastamosing network 

 in the nectaries. This phloic vascularization of nectaries has been described 

 for certain Compositae by Frei (1955) and need not be detailed here. In many of the 

 taxa studied here, phloem strands could be seen to branch from exterior achene 

 bundles at the achene top and terminate freely at the base of pappus bristles. 

 The addition of phloic bundles to the vasculation drawings would have made 

 them complex beyond interpreting, and would have added no critical features 

 not also exhibited by xylem. Phloem has therefore been omitted in the drawings 

 and xylem is used as the prime indicator of the vascular pattern of the flower. 



DESCRIPTIONS 



StenopaduSo 



This genus demonstrates the most elaborate floral venation yet found in 

 Compositae. A basic but by no means typical situation is found in Stenopadus 

 campestris (fig. 102). In the corolla of this species (fig. 102A), a pair of lateral 

 veins is found in each lobe. These extend from the tips of the lobes to the base 

 of the corolla; adjacent laterals fuse in the achene top, not in the corolla itself. 

 Occasionally (fig. 102 C, extreme right), adjacent laterals do not fuse but remain 

 separate in the achene. In addition to the laterals, median veins are present in 

 each lobe. Median veins extend for various distances into the corolla lobes. 

 If they do not extend to the tip, they terminate freely, as do the laterals; if 

 they do extend to the tip, they join with one of the laterals at the tip. Median 

 bundles extend into the achene, where they continue as five of the exterior 

 bundles (fig. 102 C). The xylem of stamen traces terminates freely in the top of 

 the achene or joins with that of corolla bundles. In details of venation, the co- 

 rolla of S. campestris resembles that found in Fitchia speciosa of the Keliantheae 

 (Carlquist 1957b). The style of S. campestris (fig. 1 B) is vascularized by a pair 

 of dorsiventrally arranged bundles; these continue into the achene (fig. 102 D), 

 joining two of the exterior bundles on opposite sides of the achene base. In 

 addition, numerous other interior bundles are present in the achene. At the achene 

 base, a lateral pair of these join with the ovule trace for a short distance (fig. 

 102 H), separating below to join exterior bundles, as do the remainder of the 

 interior bundles (fig. 102 I). Thus, there are approximately ten bundles arranged 

 in a cylinder passing from the achene base into the receptacle. The ovule trace 

 (fig. 102 D, G) branches dichotomously in the chalaza, and the adaxial portion is 

 double. 



