PLATE XLIV. 



Lesquerella spathulata. 



Fig. 51a. Spiral tracheal tubes found in the leaf trace. X 650. 



Fig. 516. Small portion of the medullary ray, as seen in cross section. 

 X 650. 



Fig. 51c. Phloem cells, as seen in cross section: A, intercellular spaces. 

 X 650. 



Fig. 52. Phloem cells, as seen in longitudinal section: A, intercellular 

 spaces. X 650. 



Fig. 53. Thin-walled parenchyma cells of the cortex, cross section. 

 X 650. 



Fig. 54. Xylem parenchyma cells, as seen in longitudinal section, x 650. 



Fig. 55. Wood fibers and tracheal tubes found in the outermost layer of 

 xylem, cross section, x 650. 



Fig. 56a. Segment of the cross section of the root, showing the consti- 

 tution of the xylem: A, wood fibers; B, tracheal elements; 

 C, wood parenchyma. X 53. 



Fig. 566. Tracheal elements found in the root: A and B, scalariform 

 tracheal tubes; C, spiral tracheal tube. X 650. 



Fig. 57. Tracheal tubes and wood parenchyma cells found in the layer 

 of xylem (fig. 56a, F) : A, tracheal tubes; B, wood pa- 

 renchyma cells. X 650. 



Fig. 58. Wood parenchyma cells, as seen in longitudinal section, x 650. 



Fig. 59. Wood fibers and tracheal tubes found in the layer of xylem 

 (fig. 56a, G). X 650. 



Fig. 60. Diagrammatic drawing of the cross section of the root, show- 

 ing: A, cork; B, collenchyma; C, stone cells; D, thin- walled 

 parenchyma; E, phloem; F, wood fibers; G, wood paren- 

 chyma; H, tracheal elements; /, medullary ray. X 65. 



Fig. 61. Cutinized epidermis of leaf: A, outer tangential wall; a, cutin- 

 ized portion; 6, cellulose portion; B, inner tangential wall. 

 X 650. 



Fig. 62. A bleached leaf, showing the method of venation: A, central 

 vein; B, lateral branches sent off from the midrib near the 

 center; C, two prominent longitudinal veins found on either 

 side of the midrib; D, E, F, terminations of veins; G, a large 

 lateral vein sent out from below the center of the midrib, 

 X27, 



