Tetramerista glabra Miq.
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Authority
Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
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Family
Theaceae
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Scientific Name
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Discussion
Wood.
Wood diffuse porous; moderately heavy, air dry specific gravity averages 0.64 with range from 0.55 to 0.72. Very little heart-sapwood differentiation in material seen but reported to have sapwood 1 to 8 mm thick that is apparent only after seasoning. Heartwood light yellowish-brown with a pinkish-brown tinge. Pores medium to moderately large-sized; in pore multiples evenly distributed in radial strings of 2 to 8 with a few groups paired tangentially to form clusters. Some chalky or gummy deposits evident in the vessels, especially in the coarse vessel lines on radial surfaces. Growth rings not visible but irregular bands of less dense tissue evident. Rays narrow and closely spaced, two sizes evident on the cross section with the larger barely distinct to the naked eye. Rays not contrasted on tangential surface but forming an inconspicuous, low, brownish fleck on radial surface. Split surfaces under hand lens magnification often appear to be entirely composed of ray tissue with the upright cells very prominent. No gum ducts or ripple marks evident.
1. Vessels. Pores large with mean tangential diameter of 225 µm (range 175 to 250 µm). Pores in radial multiples of threes (range 2 to 8) throughout most of the secondary xylem and an in multiples of 2 to 3 in the low-density zones. Approximately 10 percent of pore multiples tangentially paired to form clusters. Density of pore multiples averages 3.0 per mm2 in the usual secondary xylem, and 2.5 per mm2 in low-density zones. Pore multiples with flattened contact faces and slight constrictions between cells.
Vessel elements moderately long averaging 1.28 mm (s = 0.188 mm, sx = 0.028 mm, Cv = 14.7%). Perforations entirely simple with distinct perforation rim. Ends of elements oblique at about 45° to cell axis with a few short tails, Tyloses and gum plugs not evident. Vessel walls from 5 to 7 µm thick. No helical thickening.
Intervessel pitting alternate, minute (2 to 3 µm diameter), closely spaced but not angled through crowding. Pit apertures indistinct, horizontally elongated, and included.
Ray-vessel pitting similar to intervessel pitting with tendency to be slightly larger and more crowded, the pit apertures partially extended. Little difference between the pitting for procumbent and upright ray cells.
2. Axial parenchyma. Parenchyma abundant, apotracheal diffuse to diffuse-in-aggregates. Very evident throughout most of the secondary xylem but indistinct in low-density zones on cross section. Cells are thin-walled (1.5 to 2 µm) with average tangential diameters of 42 µm. Pitting is minute, less than 1 µm diameter, irregular, mostly evident in common end walls within strands. The fusiform strands appear to consist of 4 to 6+ cells, but are difficult to measure precisely because they mix with the upright cells in the margins of the rays.
3. Rays. Rays heterocellular, principally Kribs Type I but some approaching Type II. No uniseriate rays present. The average overall height of the rays is 1.5 mm with a range from 0.4 to 2.4 mm. Rays closely spaced, about 4 per mm, not storied. The central portions of the rays are moderately widened tangentially and are usually composed of procumbent cells, averaging 4 cells or 100 µm wide, and 11 cells or 0.5 mm tall. The procumbent cells are mostly oval to angular in tangential section and elongated radially 3 to 4 times their diameter. A few of these procumbents are larger in diameter and length and are filled more or less completely with bundles of raphides enclosed in a gelatinous sheath. The long axes of these raphides are aligned with the radial cell axis. Walls are 2 to 3 µm thick and have numerous, obvious, simple pits that exhibit anastomosing pit canals on the radial section. NY Anat Slide 127 exhibits rays in which the procumbent cells are rather short axially and some approach a square outline on the radial surface.
The marginal portions of the rays are 1- to 2-seriate, and are composed of upright cells, these margins average 6 cells high (range from 2 to 11 cells). On tangential surfaces the upright cells are usually about twice as long as wide. The walls have about the same thickness and pitting as in the procumbent cells. No cells containing raphides present.
Rays not distinctly separated especially on tangential surface because of a tendency for margins of two adjacent rays to coalesce, and for the axial parenchyma to fuse with the ray margins. 4. Fibers. Fibers long with an average length of 2.2 mm (s = 0.30 mm, sx = 0.03 mm, Cv = 9.4%). Mean tangential diameter of fibers is 45 µm with range from 34 to 58 µm. The radial diameter is smaller than the tangential. Fibers of two distinct wall thicknesses: the normal type is thick-walled with average tangential wall thickness of 14.5 µm; a thin-walled fiber type having walls about 5.5 µm thick also occurs in sporadic tangential bands of low-density, open-textured tissue. The thick-walled fibers exhibit distinct annular striations in cross sections, and have lumens that are flattened tangentially. The thin-walled fibers exhibit walls with average thickness of 5.5 µm. Pitting is sparse and minute in both fiber types, with pit chambers less than 2 µm diameter and the slit-like vertically extended apertures about 10 µm long. Fibers non-septate.
Material studied. A single wood specimen, Malayan Forest Research Institute No. 3685 from Kepong, Selangor; H. P. Brown Wood Collection No. 13959. Comparison with other published descriptions and photomicrographs indicates this is normal xylem. Slides of material from Sarawak, Borneo No. 2908, Herbarium No. 4780 and No. 3753 (NY Anat Slide 127) from Malayan Forest Research Institute.