118 THE UNIVERSITY SCIENCE BULLETIN. 



Fig. 61. Cross section of the root in region I: c, primary cortex; /, peri- 

 cycle; g, primary medullary ray; j, xylem of primary vascular bundle; b', 

 cork; m', phloem of primary vascular bundle; m", tracheal tube. X 48. 



Fig. 62. Cross section of the root in region II. Corresponding parts 

 lettered as in fig. 61: p, anomalous xylem zone; q, zone of tissue designated 

 in this article as an anomalous phloem zone; r, secondary medullary ray; 

 s, anomalous phloem; t, pericycle cells in outer part of zone of tissue desig- 

 nated in this article as a phloem zone. X 48. 



PLATE XI. 



Fig. 63. Cross section of the root in region III. Corresponding parts 

 lettered as in fig. 62: n, active arc of secondary meristem. X 48. 



Fig. 64. Cross section of the root in region IV. Corresponding parts 

 lettered as in fig. 63: g'", radial row of cells, having a radial dimension two 

 to four times their tangential dimension, in the anomalous xylem-phloem 

 zones, and having cellulose cell walls. X 30. 



PLATE XII. 



Fig. 65. Cross section of the root in region V. Corresponding parts 

 lettered as in fig. 64. X 9. 



Fig. 66. Cross section of the root in region I. Corresponding parts 

 lettered as in fig. 62. X 225. 



Fig. 67. Cross section of the root in region II. Corresponding parts 

 lettered as in fig. 62: g'", radial row of cells, having a radial dimension two 

 to four times as great as their tangential dimension, in the anomalous xylem- 

 phloem zones. 



PLATE XIII. 



Fig. 68. Cross section of the root in region III. Corresponding parts 

 lettered as in fig. 62. X 225. 



Fig. 69. Cross section of the root in region IV. Corresponding parts 

 lettered as in fig. 62: m", inner 20 per cent of anomalous xylem zone, made 

 up entirely of wood fibers; n", outer 80 per cent of the anomalous xylem zone, 

 of the usual structure found in anomalous xylem zones of the stem. X 225. 



Fig. 70. Portion of cross section of the root in region III, showing arc 

 of secondary meristem, n, in the pericycle, /. X 330. 



PLATE XIV. 



Fig. 71. Cross section of the leaf mapping out the zones of tissue: a, 

 epidermis; b, collenchyma; c, photosynthetic tissue; d, water-storage tissue; 

 e, border parenchyma; /, vascular elements, m'", lobe of the leaf. X 48. 



Fig. 72. Portion of cross section of the leaf through the main rib. Cor- 

 responding parts lettered as in fig. 71: k', cuticle: m', phloem; o', xylem; 

 p', intercellular space; d'", sieve tube having thick walls; e'", palisade layer 

 of the photosynthetic tissue; 7n"', mesophyll parenchyma just beneath the 

 palisade layer; n'", mesophyll parenchyma located between the water-storage 

 tissue and the lower epidermis. X 330. 



