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



6. A. macrostachya var. robitstior. The roots observed in this variety are 

 similar to those of the above variety, but diver in the following respects. Two, 

 rather than one, exodermis layers are present. The parenchyma sheath around 

 the endodermis is two cells wide at points. The two roots observed were 13-arch 

 with 18 central vessels and 15-arch with 16 central vessels respectively. The 

 central vessels cannot be differentiated from the peripheral ones at all points. 



7. A. sprucei (fig. 1). The cortex of roots of this species is quite distinctive 

 in consisting of only two cell layers internal to the exodermis. The outer of 

 these layers is composed of quite large cells, the inner of smaller cells which 

 ensheath the endodermis. Plates of small arm-parenchyma cells interrupt this 

 condition in places. The endodermis consists of cells thickened in a peculiar 

 fashion, so that the lumen is turbinate as seen in transectional outline. Rarely, 

 the endodermis is two-layered (two such instances are seen in figure 1) to the 

 extent of one or two pairs of cells per stele. The root examined was 7-arch with 

 a central vessel. The pericycle is not interrupted by peripheral vessels. 



Achlyphila. 



In respect of exodermis and cortex structure, the root of Achlyphila disticha 

 (fig. 7) conforms to the pattern outlined above. The endodermis, which stains 

 bright orange-red (rather than pink, as in Abolboda) with safranin, possesses 

 U-shaped thickenings not exactly like any mentioned above. The endodermis 

 may be two cells wide in places, although this condition is rare and localized. 

 Two roots examined proved to be 11-arch and 13-arch respectively. No central 

 vessels are present. This is surprising in view of the large diameter of the 

 vascular core. Instead, one to several cells that have the wall-thickening and 

 staining characteristics of endodermis cells (figure 7, dark -area in center of 

 vascular core) are present in this position. On account of their characteristics, 

 they probably should be regarded as endodermal cells, despite their location. 

 Phloem groups are extremely small and are scattered among the sclerified cells 

 of the vascular core. The pericycle is not interrupted. Significantly, there are 

 two or three layers of cells (as compared to fewer in Abolboda) between the 

 pericycle and the outermost vessels. Occlusion by tannin-like materials is char- 

 acteristic of many vessels. 



Orectanfhe. 



No roots of Orectanthe were available for study. 

 Vessels. 



For each of the above species, serial longitudinal sections were prepared to 

 show the presence of vessels. All the species described above proved to have true 

 vessel elements with simple perforation plates. Vessels have been reported by 

 Solereder and Meyer (1929) in roots of Xyris lacera, X. lanata, and X. indica. 

 Likewise, Cheadle (1942) indicates vessels with simple perforation plates for 

 roots of Xyris flexuosa and X. smalliana. 



Discussion. 



The species of Abolboda described here offer no features not previously 

 mentioned by Solereder and Meyer for Abolboda or Xyris. The possibility that 



