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9. Vertical section of the dome-shaped trunk of Stig-
. 11. Fragment of a branch of Stigmaria, showing the
character of the Tubercles, which formed articulations with the bases of the leaves. The enlargement of the leaf towards its base (a) seems to have been calculated to strengthen this part, and to afford space for the articulating socket. This socket formed, with the spherical tubercle, a universal ball and socket joint, admitting of motion in every direction to a long cylindrical leaf floating in water. Scale one-half. (Sternberg.)
Appearances presented by longitudinal and transverse sections of recent and fossil Coniferous woods, cut into thin slices, and magnified 400 times. (Nicol.)
1. Longitudinal Section of Pinus Strobus, cut paral-
a. a. Portions of concentric annual layers.
3. Longitudinal Section of Araucaria Cunninghami. 4. Transverse Section of the same.
Explan ATION OF PLATE 57. 97
Fig. 5. Longitudinal Sections of Araucaria excelsa, showing polygonal disks, in double and triple rows, on the surface of the longitudinal tubes. Some of the tubes are without disks, as in all Coniferae. Fig. 6. Transverse Section of Araucaria excelsa. a. Portion of concentric annual layer. Fig. 7. Radiating and concentric structure of a branch of Pinus, as seen by the naked eye in a transverse section; the microscopic reticulations are omitted (See V. I. p. 365. Note.) a. a. Concentric annual layers, indicating periodical growth. Fig. 8. Longitudinal Section of Pinus, showing the relative positions of the longitudinal vessels and medullary rays. a, Longitudinal vessels, forming the woody fibres. b, Medullary rays.
Plate 57. V. I. p. 371.
Sections exhibiting the silicified remains of Coniferae and Cycadeae, in their native bed, between the Portland and Purbeck stone, on the coast of Dorsetshire. Fig. 1. Appearance of trunks and roots of large Coniferous trees, and of trunks of Cycadites, in the black earth, which formed the soil of an ancient Forest in the Isle of Portland. (De la Beche.) Fig. 2. Remarkable concentric Ridges of Stone, around the erect stump of a Fossil Tree in the Isle of Portland. See W. I. p. 372. Note. (Henslow.) Fig. 3. Inclined position of the petrified stumps of large Coniferae, and of the bed of black mould and pebbles in which they grew, near Lulworth Cove, on the Coast of Dorset. (Buckland.)
PLATE 58. V. I. p. 370.
Cycas revoluta, producing Buds from the axillae of the scales, or persistent bases of leaves, that form the false bark. Drawn from a plant in the conservatory of Lord Grenville at Dropmore, 1832.
PLATE 59. W. I. p. 371.
Fig. 1. Zamia pungens, with its fruit, as it grew at Walton on Thames, 1832, in the Conservatory of Lady Tankerville. (Lambert.)
Fig. 2. Transverse section of the trunk of Zamia horrida, from the Cape of Good Hope. (Buckland.)
Fig. 3. Transverse section of a young trunk of Cycas revoluta. See Geol. Trans. Lond. 1828. N. S. Vol. ii. Pt. 3. Pl. 46. (Buckland.)
PLATE 60. W. I. p. 373.
Fig. 1. Silicified trunk of Cycadites megalophillus, from the Dirt bed in the Isle of Portland. (Original.) Fig. 2. Portion of the base of Fig. 1. See W. I. p. 373, Note. (Original) In Plates 60, 61, A represents the central mass of cellular tissue. B the single circle of radiating woody plates. C the circle of cellular tissue, surrounding B. And D the case or false Bark, surrounding C. And in Pl. 61, Fig. 1, b, represents a second circle of radiating woody plates.
PLATE 61. W. I. p. 373. Note.
Fig. 1. Silicified trunk of Cycadites microphyllus, from the Isle of Portland, with numerous buds rising from the axillae of the Petioles. (Original.)
ExPLANATION OF PLATE 62. 99
Figs. 2, 3. Vertical sections of agatised Petioles, composing the false bark on the trunk of Cycadites microphyllus, and of embryo Buds. In the Bud, Fig. 2. d. the division between the two woody circles is not distinct. In Fig. 3'. d. it is very obvious; but the intermediate circle of cellular tissue is represented only by a fine line. See W. I. p. 374, Note. and p. 376, Note. (Original.) In the sections of Pl. 61, Figs. 2, 3, and Pl. 61, the following letters are used to indicate the same parts. a, cot
ton, or down; b, integument of petioles or scales; c, bundles of vessels; d, woody circles; e, imperfect woody
Fig. 1. Longitudinal section of a Petiole of Zamia spiralis magnified two times. It exhibits four bundles of • vessels passing longitudinally through the cellular tissue, which is interspersed with gum vessels. V. I. p. 375. (Original.) A. Transverse section of Fig. 1. magnified, and showing the irregular disposition of the bundles of vessels. (Original.) c'. Magnified view of one of the bundles of vessels at A, c. (Original.) B. c.". Magnified transverse section of a bundle of vessels in the petiole of Zamia horrida. (Original.) Fig. 2. Longitudinal section of a portion of an agatised petiole of Cycadites microphyllus, from Portland, magnified four times. The down or cotton at a, is
* These very beautiful and instructive sections were presented to me by Mr. Witham, being portions of a trunk which I had placed at his disposition.
most beautifully preserved, and the integuments of the petiole b, longitudinal vessels e, and gum vessels J, correspond with those in Fig. 1. See W. I. p. 375, Note. (Original.)* Fig. 3. Transverse section of a portion of the lowest Petioles, in Pl. 61, Fig. 3, b, c, magnified four times. The disposition of the bundles of vessels is nearly parallel to the integument of the Petiolet d, Magnified portion of the double woody circle, within the Embryo bud, Pl. 61. Fig. 3. 'd. d'. More highly magnified portion of the embryo double woody circle d. c'. More highly magnified section of one of the bundles of vessels, adjacent to c. These bundles of vessels, exhibit, in their transverse Section, a series of minute tubes, arranged in rows, and between these rows, opaque plates of compressed cellular tissue, resembling portions of medullary rays. The fibrous structure of the integument is preserved in several parts of b. See V. I. p. 376, Note. (Original).
* Mr. Robert Brown has noticed in the cellular tissue of a silicified trunk of Cycadites, portions of Calcedony bearing the form of extravasated gum within the trunks of recent Cycadete. He has also recognised spiral vessels, in the laminated woody circle of a mature trunk of fossil Cycadites, and also in the laminated circle within a silicified bud of the same, near its origin.
# A familiar example of a nearly similar disposition of bundles of vessels, passing into the Petiole or leaf-stalk, may be seen in the base of the fresh fallen leaves from a horse-chestnut tree, or in the scars on a cabbage-stalk, from which leaves have fallen off.