102 THE UNIVERSITY SCIENCE BULLETIN. 



THE ROOT. 



The root is a taproot, light brown in color, with approximately 

 the same length and diameter as the main axis of the stem, and 

 having only a few lateral roots attaining much size. Many very 

 small rootlets, with suberized walls for several of their outer layers 

 of cells, are retained throughout the main root. One to several of 

 these arise from each of the numerous grooves in the root. The 

 lateral roots and rootlets extend into the central xylem cylinder 

 or into the first, second or third formed anomalous xylem zone. 

 It has the same habits of growth in thickness as the stem. 



The genera] areas of tissue for regions I, II, III, IV and V are 

 mapped out in figs. 61, 62, 63, 64 and 65. The detail of tissues in 

 regions I, II, III and IV can be found in figs. 66, 67, 68 and 69. 



The resemblance in structure of the corresponding tissue of 

 root and stem is so close it is not necessary to give a detailed 

 description of the root here. In very young roots (fig. 66, b') the 

 two or more outer rows of cells become suberized to form cork. 

 Apparently no cork cambium has arisen. Later a few layers of 

 cells, located just interior to these two or more outer rows of pri- 

 mary cortex cells having suberized walls, suberize their cell walls. 

 The cells of the starch sheath can not be clearly discerned, as in 

 the stem, except in portions of certain sections. In figs. 61 and 66 

 are shown the central xylem cylinder, the phloem groups of the 

 primary vascular bundle, and the primary medullary rays. The 

 water tubes of the central xylem cylinder are large, and stand out 

 well when stained with phloroglucin (fig. 66, m"). 



Rings of arcs of secondary meristem arise successively in the 

 pericycle, as in the stem, and form anomalous xylem-phloem zones. 

 An arc of secondary meristem is shown in fig. 70. In region II 

 (figs. 62 and 67) the anomalous growth has begun, and a second 

 xylem-phloem zone is starting to form in region III (fig. 63); and 

 the fourth zone, in region IV (fig. 64). From eight to ten xylem- 

 phloem zones are present in region V (fig. 65) ; ten to fourteen in 

 the region of the main root having the greatest diameter. 



The zones of the anomalous structure are more nearly concen- 

 tric and broader radially than in the stem. The anorqalous zones 

 anastomose both tangentially and radially, but the anastomosis 

 of the first three xylem-phloem zones is not so frequent as in the 

 corresponding zones of the stem. The three innermost xylem- 

 phloem zones of the anomalous structure are more nearly con- 

 centric than in the stem (fig. 64). The number and arrangement 



