PRATT: CYCLOLOMA ATRIPLICIFOLIUM. 93 



thick for this region. This feature is discussed later. The central 

 strip of procambium and the young water tubes of the primary 

 xylem can be clearly discerned (fig. 29, i' and a'"). Immediately 

 down the stem from region I the leaf-trace bundles appear in the 

 pericycle (fig. 31, k), where they are crossing out into the leaf, 

 and the cambial layer of the primary vascular bundles is discern- 

 ible (fig. 31, n'). Some secondary phloem and xylem have been 

 formed by the cambial layer in region II (fig. 32, m' and o'). 



In longitudinal sections of region III the sieve tubes, the com- 

 panion cells and the phloem parenchyma cells are discernible, as 

 shown in figs. 33 and 34, h'" and c'". In cross section the sieve 

 plates are difficult, to distinguish, their pits being very small 

 (fig. 34, d'" and /'")• Certain sieve tubes have thickened their 

 cell walls (fig. 34, d'") and others have not (fig. 34, /'"). The 

 cambium is active yet in a few of the bundles. Spiral and annular 

 tracheae of primaiy xylem are shown in figs. 36, 37 and 38. The 

 parenchyma of primary xylem does not lignify. 



In the secondary xylem of the primary vascular bundles the 

 tracheae have circular lumina, and are prominent. The tracheae 

 are pitted, having slightly elongated, bordered pits (fig. 39), or 

 are of reticulate type (fig. 40). Solereder ('08) states, the tracheae 

 in the Chenopodieae usually have simple pits, but mentions the 

 genus Axyris as an exception. Georghieff {fide Solereder, '08) 

 records scarlariform perforations with oblique, almost longitudinal, 

 bars in Axyris amarantoides. At intervals portions of the cross walls 

 of the elements of the tracheae remain (fig. 39). The wood paren- 

 chyma cells of the secondary xylem of the primary vascular 

 bundles are ordinary in size and shape, and have few and only 

 inconspicuous pits (fig. 41). Wood fibers were not found to occur 

 in the xylem of the primary vascular bundles. The fiber tracheids, 

 which are rather few, vary in size and shape, and have bordered 

 pits (fig. 42). 



In the primary vascular bundles of region IV (fig. 43, m' and o') 

 more secondary phloem and xylem are present than in the cor- 

 responding bundles of region III. The wood parenchyma of the 

 secondary xylem of these bundles in this region of stem is well 

 lignified. 



A leaf-trace bimdle with an active cambial layer is shown in 

 fig. 31, k, and an older leaf-trace bundle in region IV is shown in 

 fig. 44. The leaf -trace bundles do not grow to be very large. The 

 cambial layer in most of the leaf -trace bundles of region III has 

 ceased its activity. Solereder makes the following statement con- 



