90 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [VOL. 10 



9. A. spriicei (fig. 52). The inflorescence stem of this species shows no 

 features not indicated above, bur illustrates the generic characters rather 

 clearly. The cortical zone of this axis is composed of spherical chlorenchyma 

 cells. Exterior to the sclerenchyma ring is a circle of bundles; this circle is 

 enveloped by a layer of non-photosynthetic parenchyma. The outermost layer 

 of the scelerenchyma ring is very thick walled, and several less prominently 

 sclerified cell layers occur internal to it. All the central bundles occur in the 

 thin-walled ground tissue, although some are adjacent to the sclerenchyma ring. 

 Bundles are of the graminean type or transitional to that type from the 

 ordinary collateral. 



Orectanthe. 



An inflorescence axis of only one species. 0. sceptrum (fig. 55), was sec- 

 tioned. This stem showed a number of noteworthy features. A sclerified epidermis 

 is present. Beneath this are about two cell-layers differentiated as a hypodermis. 

 The remainder of the cortical zone consists of spongy " chlorenchyma. Within 

 the chlorenchyma are a number of bundle*, most of which have a sclerenchy- 

 matous sheath. The sclerenchyma ring contains a number of bundles, not dis- 

 posed in concentric circles. The thin-walled ground tissue intergrades into the 

 sclerenchyma ring. Bundles of the scleronchyma ring and central ground tissue 

 are intermediate between amphivasal and collateral patterns. 



Achlyphila. 



The markedly flattened inflorescence axis of this genus (fig. 44) suggested 

 that more or less prominent differences from Abolboda would.be present. In 

 fact, despite the obvious differences in shape, the similarities are perceptible. 

 To be sure, the epidermis (which is two-layered in places at the edges of the 

 axis) is heavily sclerified. Then. too. bundles (each with a fibrous sheath) 

 occur in the cortical region on each edge of the axis. Aside from these differences, 

 one can cite similarities in the chlorenchyma : two layers of palisade and 

 several spongy layers are present. Adjacent to the outer margin of the scle- 

 renchyma ring — or "ellipse" — bundles are present, each sheathed by a single 

 layer of fibers along the outer surface, as in Abolboda. Bundles are present in 

 the sclpren^hyma. toward the inner margins of its extent. The central ground 

 tissue consists of thin-walled parenchyma and (unlike Abolboda, but like Xyrxs) 

 contains no bundles. The last-cited feature suggests that the resemblances of 

 Achlyphila may lie closer to Xyris than to Abolboda. 



Because Achlyphila is unique among Xyridacrae in not having a congested 

 inflorescence, elongate pedicels are present. As is shown in figure 82, the pedicel 

 is triangular in outline. Like the inflorescence axis, the pedicel has a sclerified 

 epidermis. Two circles of bundles, one adjacent to the inner margin of the 

 sclerenchyma ring (or, at lower levels, just within the ring) may be found. A 

 central zone of thin-walled parenchyma is present. 



Discussion. 



The above descriptions must not be construed as exhibiting the full range 

 of variation either in a species or in an individual axis, although an attempt 

 is made to suggest the nature of such variation Because of this variability. 



