1(U 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[VOL. 10 



of Mutisieae. Because of this fact and the infrequency of such canals in the 

 tribe (see Solereder, 1908, for a list of Mutisieae in which they do not occur), 

 the phylogenetic interpretation is not clear. The presence of unorganized inter- 

 cellular deposition of resinous products may represent a stage before develop- 

 ment of organized canals, or it may represent a substitution for such canals 

 following their loss phylogenetically. 



Node and Petiole. The following numbers of leaf gaps were found for the 

 genera of Guayana Mutisieae : 



Stenopadus: 5 Gong ylole pis : approximately 7 



Stomatochaeta : 3 Achnopogon : 3 



Chimantaea : 5 Vuidaea: 3 



Quelchia: 3 Xeblinaca : 5 



Glossarion : 5 



Considering that this group is fairly closely-knit, these divergences among 

 genera within close alliances is noteworthy, and may probably best be explained 

 on the basis of habit and leaf morphology in each genus. For example, the wide, 

 sheathing bases of Gongylolepis leaves might be expected to be connected with 

 a multilacunar condition, whereas the narrow or needle-like leaves of Duidaea 

 seem correlated with a trilacunar situation. The phylogenetic significance of 

 these differences, however, is difficult to interpret in the lack of adequate data 

 for nodal conditions for the family. Both trilacunar and multilacunar nodes 

 have been reported for the family (Sinnott 1914). It may be noteworthy in 

 this connection that putatively primitive members of Ileliantheae possess multi- 

 lacunar nodes (Carlquist 1957d). 



In genera with sessile leaves (Stomatochaeta, Achnopogon^ Duidaea) little 

 branching of traces takes place in the cortex subtending the leaf, or in the leaf 

 base. In the petiolate taxa, however, the traces branch into a simple arc of 

 numerous bundles in the petiole base. Lateral bundles of this arc may be 

 branched in their extent in the cortex, shortly above their departure from the 

 vascular cylinder. The disposition of fibers around leaf traces in the cortex, 

 mentioned earlier, continues in the petiole, and becomes altered into bundle 

 sheaths, considered below. 



II. LEAF 



The Guayana Mutisieae are notable for excessive complication in leaf anatomy. 

 The only other member of the tribe for which leaf anatomy has been described 

 in detail, Hespcromannia (Carlquist 1957c) is much simpler by comparison. 

 Hesperomannm has a mesophyll undifferentiated into palisade and spongy tissue, 

 and is otherwise unspecialized except in its sunken biseriate hairs. 



Leaves of the genus Stenopadus (figs. 8-11) show examples of complicated 

 leaf structure, as well as demonstrating considerable specific differentiation in 

 anatomical details. Leaves in this genus all have a thick cuticle on both surfaces 

 and relatively thick leaves, but vary in : relative thickness of mesophyll ; presence 

 or absence of a hypodermis on adaxial or abaxial surface, and thickness of it ; 

 number of palisade and spongy layers, if differentiated. These features may be 

 conveniently summarized in tabular form (figures for spongy and palisade are 

 approximate). 



