LIST OF ILLUSTRATIONS AND EXPLANATION OF PLATES. 51 



EXPLANATION OF PLATES.* 



Key to index-letters on figures (except figs. 47-51). 



a, initial cell. ip, inner pericycle. r root 



c, cortex. iph, inner phloem. r fi root-hair 



cy, conjunctive parenchyma. is, inner sclerenchyrna. r f rootlet 



e, epidermis. ist, inner starchy tissue. *, sclerenchvma 



/, fundamental tissue. Wf endodermis. sa air-space 



A, hypodermis. p, pericycle. gp spiral tracheid. 



i, rhizogenous cell. pa, parenchyma. <, starchy tissue. 



ic, inner fundamental tissue. ph, phloem. I tracheid 



icj, inner conjunctive paren- p(, plerome. v , sieve-tube. 



chyma. pph, protophloem. x xylem 



in, inner endodermis. px, protoxylem. 



Letters used variously: b, d, m, o, u, tr, 1, 2, 3, etc. 



PLATE r. 



1. Habitat of D. punctilobula; Massachusetts. Photo by C. E. Waters, Ph.D. 



2. Leaves as they grow. From Waters, 1903, by courtesy of the author and publishers 



PLATE 2: 



3. Rhizome, natural size, showing fork, leaf bases, and leaf-shoots. 



4. Leaf-bud with two unequal leaf-shoots, natural size. 3 and 4 from photo by 



C. E. Waters, Ph.D. 



5. Portion of pinna showing pinnules, lobes, crenations, sori, and hairs. X about 



10. From Waters, 1903, by courtesy of the author and publishers. 

 PLATE 3: 



6-8. Diagrams showing distances between rootlets, natural size. 



9. Diagrammatic projection of a piece of stem 5 cm. long, including apex, with 



figures to indicate the number of roots attached to each eighth of the 



circumference. 



10-13. Diagrams of divisions of ro^t-cap segment as seen from distal side. 

 14. Diagrammatic longitudinal section of root-tip, showing the origin of the various 



tissues. Walls numbered in order of formation. 

 15-22. Diagrams of division in segments of root initial. Walls numbered in order 



of formation. 

 PLATE 4: 



20-22. See above. 



23. Root-tip in longitudinal section. X 210. 



24. Longitudinal section of an anomalous root-cap, showing two layers from one 



segment at point marked *. X 210. 

 25-32. Successive transverse sections of a root-tip. 25, 26 in cap; 27-32 in root; b 



indicates root-cap. Initial and second set of segments dotted. All in 



the same relative position. X 210. 

 PLATE 5: 



28-32. See above. 



33. Transverse section of same root, o.i mm. farther up than 32; b, root-cap. X 210. 



34. Rhizogenous cell, undivided, in transverse section of root. X 210. 



35. Rhizogenous cell, second division, in similar section. X 210. 



PLATE 6: 



36. Rhizogenous cell, third division. X 210. 



37. First division in rhizogenous cell; longitudinal radial section of root. X 210. 



38. Endodermis with rhizogenous cells, tangential view. Reconstruction from 



serial longitudinal sections of root. X 210. 



39. Ditto: another root. X 210. 



40. Oblique tangential view of rhizogenous cell, showing its first three divisions. 



X 210. 



41. Rootlet initial from longitudinal tangential section of root. X 210. 



42. Rootlet initial in transverse section of root; one cap-layer. Cells within the 



chain of arrows have arisen by proliferation of cortex. X 210. 



43. Ditto; two cap-layers, , and digestive layer of cortex, o. X 210. 



44. Part of transverse section of nearly mature root. X 210. 



45. Transverse section of stele of fully mature root. X 210. 



46. Part of transverse section of old root with outer layers shedding off. X 100. 



*A11 figures are of Qennvoetdtia punQtUobula unless otherwise stated in the description. 



