PRATT: CYCLOLOMA ATRIPLICIFOLIUM. 103 



of tracheae for unit areas in cross sections is the same as in the 

 xylem zones exterior to the innermost anomalous xylem zone of 

 the stem, but there are relatively more tracheae having the larger 

 diameter (fig. 65). Commonly the part of the xylem lying on the 

 inner side of the zone is made up entirely of wood fibers (fig. 

 69, m"), and about 80 per cent of the xylem zone has the usual 

 sti-ucture found in the xylem zones of the stem (fig. 69, 7i"). The 

 walls of the pericycle cells included in each phloem zone lignify 

 slightly. The cell walls of the secondary medullary rays usually 

 remain cellulose. 



Traversing the anomalous zones in cross sections of the root, as 

 in cross sections of the stem, are the radial rows of cells having a 

 radial dimension from two to four times as great as their tan- 

 gential dimension (figs. 65, g'", and 69, g'"). In the zones of 

 tissue designated as phloem zones in this article these cells are 

 pericycle cells and secondary medullary ray cells; in the xylem 

 zones these cells resemble wood parenchyma in size and proportion. 

 The walls of many of these cells are lignified, as are the walls of 

 similar cells in the stem; but all these cells in certain sections of 

 the root have cellulose walls, and in many regions of the root are 

 in direct connection with the vascular elements of the veiy small 

 rootlets, which extend from the exterior grooves into the central 

 vascular cylinder or inner anomalous xylem zones of the main 

 root. The absorbed water is readily transmitted by these cells, 

 included in the radial strips, to all parts of this region of root. 



THE LEAF. 



The leaves of Cycloloma atriplicifolium are alternate and oblong- 

 elliptic, with pointed lobes. Like the stem, the leaves are colored 

 a light green, and are purplish tinged. The leaf is not unusual in 

 structure, and possesses many of the leaf characteristics of the 

 Chenopodieae mentioned by Solereder ('08). The areas of tissue 

 in a cross section of a typical leaf are mapped out in fig. 71. 



The epidermal cells are much more irregular in shape, as seen 

 in cross section, than in the stem (figs. 72, a, and 73, a). The cells 

 of the upper and lower epidermis are shown in surface view in 

 figs. 74 and 75, and the lengthened cells of the upper epidermis 

 over the main rib are shown in fig. 76. The cell walls of the epi- 

 dermis are cellulose, except the cuticle, which reaches a thickness 

 of only .001 mm. Solereder ( '08) states that in spite of the xe- 

 rophilous character of many species of Chenopodieae, the cuticle 

 rarely attains a considerable thickness. 



