1960] 



ANATOMY OF QUAY AN A XYRIDACEAE 



71 



endodermis-cell characteristics could be used as specific characteristics, sug- 

 gested by Malme in 1925, appears to be valid. Maline shows very thick-walled 

 endodermal cells with centrally placed lumina for A. pulchclla and A. vaginata. 

 He reports prominent thickenings on the inner wall, tapering sharply on the 

 radial walls, and absent on the outer walls, for endodermal cells in roots of 

 A. pocppigii. A. grandis, and A. macrostachya. Malme 's figure for A. macro- 

 stachya is markedly different from the condition illustrated here for that species. 

 The endodermal cell thickenings Malme reports for A. poarchon and A. abbre- 

 viata are like those illustrated in the present study for A. acicularis. 



Interestingly. Malme 's figures all show an uninterrupted pericycle (A. vagi- 

 nata, A. macrostachya, A. poarchon). The species of Abolboda in the present 

 study in which uninterrupted pericycle was observed all belong to the group 

 termed "larger-stemmed abolbodas"' in sections below. Malme 's figures also 

 suggest a larger number (six or more) of xylem poles, a feature also character- 

 istic of the group just named. Thus as Malme (1925) claims, different types of 

 root anatomy in Abolboda appear to be characteristic of species or species- 

 groups; from the example of A. spruce* described above, one may surmise that 

 such characters are not always limited to the stele, but may be found in the 

 cortical zone as well. 



The several layers of cells between endodermis and outermost vessels, the 

 absence of central vessels, the presence of endodermis-like cells in their place, 

 and the distinctively staining endodermis thickenings are characteristics which, 

 taken together, would seem to give the roots of Achlyphila a generic differentia- 

 tion from the other three genera. In fact, some of these characteristics seem 

 new to Xyricfaceae, although the sum of characteristics in this genus would not 

 exclude it from the family. 



On the basis of the present study, one may conclude that the roots of 

 Abolboda olfer no anatomical features (other than greater size, and therefore 

 more numerous vessels) which cannot also be found in Xyris roots, as the 

 account of Solereder and Meyer (1929) illustrates. 



stem 



As the summary of Solereder and Meyer shows, remarkably little is known 

 about stem anatomy in Xyridaccac. The only facts that have been established 

 are that bundles are amphivasal. individual bundles may be sheathed with 

 sclerenchyma (incompletely in X. lanata), and that (in X. Janata) the bundles 

 may form concentric bands. As an additional generalization, the writer would 

 like to add the fact that in all taxa he examined, vascular bundles tend to be 

 more or less amphivasal except where they are demarcated as leaf traces, in 

 which case the structure of the bundles tends to be more nearly collateral. 



The data given below are derived from study of mature portions of rosette 

 stems, except for Achlyphila, which has a rhizomatous habit. At and near the 

 base of a stem, especially in the smaller-stemmed species of Abolboda, departing 

 roots may be numerous in the cortex, and the vascular bundles may form a very 

 small group in the center of the stem. In A. am erica na, no part of the stem 

 (except the very youngest) was free from departing roots. The types of stem 

 anatomy observed in the Xyriduceae under study here fall into four main groups. 



