234 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
Plate 
XXVIII. fig. 34. Diploxylon , segment of a transverse section of_fig. 33, magnified 15 
diameters. 
XXIX. fig. 35. Sigillaria , transverse section of the epidermal layer of the bark, mag- 
nified 4 diameters. 
„ fig. 36. Sigillaria , one rib of fig. 35, enlarged 13 diameters. 
XXVIII. fig. 37. Sigillaria , radial section made along the centre of one of the raised 
longitudinal ribs of fig. 35, magnified 4 diameters. 
„ fig. 38. Sigillaria , portion of fig. 37, enlarged 12 diameters. 
XXIX. fig. 39. Sigillaria , part of the surface of the specimen. Mr. Nield. 
,, fig. 40. Sigillaria , transverse section of the epidermal layer of fig. 39, natural 
size. 
XXX. fig. 41. Sigillaria , a segment of fig. 40, enlarged 15 diameters. 
XXIX. fig. 42. Sigillaria, vertical section through the centre of a part of one rib of 
fig. 39, showing the vascular bundle going to the base of the petiole, mag- 
nified 15 diameters. 
XXX. fig. 43. Stigmarian root, radial section of the innermost part of the woody 
zone, with a medullary ray and vascular bundle going off towards a rootlet, 
magnified 13 diameters. Mr. Whittaker. 
XXIX. fig. 44. Stigmarian root, radial section like fig. 43, but of the outermost part 
of the ligneous zone, with medullary ray and vascular bundle, magnified 
10 diameters. 
„ fig. 45. Stigmarian root, tangential section of part of the ligneous zone, with one 
primary and numerous secondary medullary rays, magnified 13 diameters. 
„ fig. 46. Stigmarian root, part of fig. 45, with secondary medullary rays, mag- 
nified 50 diameters. 
XXX. fig. 47. Stigmarian root, transverse section of the innermost part of the woody 
zone, with a medullary ray and vascular bundle going to a rootlet, magnified 
15 diameters. 
„ fig. 48. Stigmarian root, outer surface of the ligneous zone, with the peripheral 
extremities of the primary medullary rays and vascular bundles of the 
rootlets, magnified 4 diameters. Mr. Whittaker’s cabinet. 
„ fig. 49. Stigmarian root, radial section of the innermost bark, magnified 120 
diameters. 
XXXI. fig. 50. Stigmarian root, tangential section of the middle bark, magnified 100 
diameters. 
XXX. fig. 51. Stigmarian’root, bases of three rootlets, with the epidermal layer upon 
which they are implanted, magnified 3 diameters. 
XXXI. fig. 52. Stigmarian root, base of one rootlet, magnified 6 diameters. Mr. Nield. 
„ fig. 53. Stigmarian root, diagram representing a restoration of the entire root, 
with the surfaces of the pith, wood, and bark successively displayed in the 
