PRATT: CYCLOLOMA ATRIPLICIFOLIUM. 115 



innermost anomalous xylem zone; d', anomalous xylem of the usual structure 

 in the outer portion of the innermost anomalous xylem zone. X 225. 



Fig. 27. Longitudinal section of primary medullary ray cells from 

 region III of the stem. X 225. 



Fig. 28. Longitudinal section of pith cells from region III of the stem. 

 X 225. 



PLATE VII. 



Fig, 29. Diagram of a longitudinal section of the main axis of the stem 

 to show the location of the five regions of stem, the broken leaf traces of 

 region V and below, and the anomalous xylem-phloem zones; j, primary 

 vascular bundle; 7i, arcs of secondary meristem anastomosing radially with 

 the arcs, in the corresponding ring of secondary arcs, in the region of stem 

 below; p, anomalous xylem zone; q, tissue designated in this article as an 

 anomalous phloem zone; u, radial strip of xylem anastomosing from one 

 anomalous xylem zone to another; g', radial strip of tissue anastomosing 

 from one anomalous phloem zone to another; h", fruit; i", leaf; j", branch; 

 k", region of primordial meristem; I", procambium; m", region I; n", region 

 of the stem for fig. 31; o", region I; p", region III; q", region of the stem for 

 figs. 50 and 51; r", region IV; s", region V; /", leaf trace of leaf retained; 

 u", broken leaf trace. 



Fig. 30. Primary vascular bundle in the formation in region I of the 

 stem: /, inner area of pericycle; g, primary medullary ray; h, pith; h', pri- 

 mary phloem; i', procambium; /, primary xylem; a'", water tube. 



Fig. 31. Cross section of the stem just below region I (location shown 

 in fig. 29, n"), showing young leaf trace bundle, k, in pericycle. Correspond- 

 ing parts lettered as in fig. 8. X 225. 



Fig. 32. Primary vascular bundle with cambial layer from region II of 

 the stem. Corresponding parts lettered as in fig. 8. X 330. 



Fig. 33. Longitudinal section of sieve tubes from secondary phloem of 

 primary vascular bundle in region III of the stem. X 330. 



Fig. 34. Longitudinal section of companion cells, b'", and phloem pa- 

 renchyma c'", of a primary vascular bundle in region III of the stem. X 330. 



Fig. 35. Primary vascular bundle, in which the cambial layer is no 

 longer active, in region III of the stem. Corresponding parts lettered as in 

 fig. 32: d'", sieve tube having thickened cell walls; /'", sieve tube with cell 

 walls not thickened. X 330. 



Fig. 36. Longitudinal section of a small spiral tracheal tube from pri- 

 mary xylem in region III of the stem. X 225. 



Fig. 37. Longitudinal section of larger spiral tracheal tube from pri- 

 mary xylem in region III of the stem. X 225. 



Fig. 38. Longitudinal section of annular tracheal tube of medium size 

 from primary xylem in region III of the stem. X 225. 



Fig. 39. Longitudinal section of pitted tracheal tube of medium size 

 from a primary vascular bundle in region III of the stem. X 225. 



Fig. 40. Longitudinal section 'of reticulate tracheal tube of medium size 

 from a primary vascular bundle in region III of the stem. X 225. 



