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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[VOL. 10 



Vessels. 



Although Solereder and Meyer (1929) do not mention the occurrence of 

 vessel elements in leaves of Xyridaceae, longitudinal sections of leaves revealed 

 vessel elements with simple perforation plates in the following species : Abol- 

 boda linearifolia, A. macrostachya var. angustior, A. macrostachya var. macro- 

 stachya, and A. macrostachya var. robust ior. Vessels, therefore, definitely do 

 occur in leaves of at least the larger-leaved species of Abolboda. Vessels with 

 simple perforation plates are indicated by Cheadle (1942) for leaves of Xyris 

 flexuosa and X. smalliana. 



INFLORESCENCE AXIS 



Solereder and Meyer (1929) have concluded that Xyris differs from Abolboda 

 in the general structure of the inflorescence axis. Xyris, according to these 

 authors, possesses bundles embedded in (rarely outside of) the sclerenchyma 

 ring, whereas Abolboda has bundles scattered through the central ground tissue 

 ("pith") as well. This contrast appears to be justified on the basis of the 

 present study. Solereder and Meyer also claim that bundles of the graminean 

 type are absent in the inflorescence axes of Abolboda although they are present 

 in Xyris. I have found that the more basal portions of inflorescence stems in 

 Abolboda tend to have "ordinary" collateral bundles, or ones which are some- 

 what amphivasal. At higher levels, the graminean-type bundles were seen in 

 "pith" of all the taxa considered here except Abolboda acicularis, A. americana, 

 and Achlyphila disticha. 



Abolboda. 



Variables within a single inflorescence axis of Abolboda include the relative 

 presence of photosynthetic tissue and the thickness of the sclerenchyma ring. 

 Chlorenchyma appears to be absent from those portions of the axis most distal 

 and most proximal to the base of the plant. Chlorenchyma, where present, con- 

 sists of nearly spherical cells; some may be somewhat elongate radially, and 

 form a palisade. If chlorenchyma is not present, parenchyma cells polygonal 

 in outline in transection (elongate in longitudinal section) extend from the 

 epidermis to the sclerenchyma ring. If chlorenchyma is present, a single layer 

 of non-photosynthetic parenchyma is often present outside the sclerenchyma 

 ring. If cnlorenchyma is present, a single layer of non-photosynthetic par- 

 enchyma is often present outside the sclerenchyma ring, particularly at those 

 points where bundles are adjacent to the outer face of that ring. The scleren- 

 chyma ring consists of several layers of thick-walled lignified cells. The outer- 

 most may have much thicker walls than layers internal to it. 



1. A. acaulis. Because of the nearly sessile habit of the inflorescence in this 

 species, no structure comparable to the inflorescence axis in the other species 

 can be studied. 



2. A. acicularis. This species (fig. 49) shows a number of features typical 

 for the genus. Within the epidermis, both palisade and spongy palisade 

 chlorenchyma occur. The single layer of non-photosynthetic parenchyma out- 

 side the sclerenchyma ring is ordinarily present. The outer face of each of 

 the bundles (about 7) which occur outside the ring is sheathed by a single 

 layer of sclerenchyma. No bundles occur within the sclerenchyma ring itself, 



