Characteristics of the xylem

In the present material, the genera Buxus, Pachysandra, Sarco-cocca, and Styloceras represent an anatomical unit. Annual rings occur in all species of the temperate zones (Buxus Fig. 1, Sar-cococca Fig. 2). Density fluctuations instead of rings occur in the tropical Styloceras brokawii (Fig. 3). Annual rings are often indistinct in Pachysandra (Fig. 4). A band of latewood with few vessels and a small band of radially flat fiber cells mark ring boundaries of most species. All species are diffuse-porous and have solitary vessels (Figs. 1-6). Vessel diameter varies between 15 and 40 pm. Vessels are extremely small (<20 pm) in Pachysandra stylosa (Fig. 4) and in Sarcococca hookeriana (Fig. 2). All species contain scalariform perforations: with few bars in Buxus

(Fig. 6), which has less than 10 while and all others more than 20 (Fig. 7). Plugs of dark-stained substances are present in vessels of Buxus sempervirens. Vessel density varies from 300-500/mm2. Intervessel pits are predominantly small and round. The radial walls of fibers are typically thick (Figs. 1, 2 and 5) and perforated by round pits with a diameter of 2-3 pm (Fig. 8). Fibers are thin- to thick-walled in Styloceras brokawii (Fig. 3). Axial parenchyma is usually apotracheal diffuse or unrecognizable (Fig. 5). The rays of both Pachysandra species are exclusively uniseriate with upright cells (Fig. 9). The rays of Buxus, Sarcococca and Styloceras have 1-2 cells (Figs. 10 and 11). Rays of Buxus sempervirens are heterocellular (1-3 marginal, square and upright cells, Fig. 10). Central cells in rays of Sarcococca and Styloceras are square in the interior and upright at the margins (Fig. 11).

Define Diffuse Porous Botany

Fig. 1. Diffuse-porous wood. Ring boundaries are defined by a zone with few vessels. Stem of a 2 m-high shrub, dry site on limestone, submediterranean climate, Niaux, Pyrenees, France. Buxus sempervirens, transverse section.

Fig. 1. Diffuse-porous wood. Ring boundaries are defined by a zone with few vessels. Stem of a 2 m-high shrub, dry site on limestone, submediterranean climate, Niaux, Pyrenees, France. Buxus sempervirens, transverse section.

Fig. 2. Diffuse-porous wood. Ring boundaries are defined by a zone with few vessels. Vessel diameter is small (<20 pm). Stem of a 60 cm-high shrub, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Sarcococca hookeriana, transverse section.

Fig. 3. Wood with indistinct rings. Zones with more or fewer vessels and thicker fiber cell walls indicate growing zones. Stem of a 1.5 m-high shrub, cultivated, tropical greenhouse, Botanical Garden Zürich, Switzerland. Styloceras brokawii, transverse section.

Fig. 2. Diffuse-porous wood. Ring boundaries are defined by a zone with few vessels. Vessel diameter is small (<20 pm). Stem of a 60 cm-high shrub, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Sarcococca hookeriana, transverse section.

Wood Transverse Section

Left Fig. 4. Diffuse-porous wood with two rings. The second is very small. Vessel diameter is small (<20 pm). Ray cells have a short radial expansion. Isolated scleren-chyma cells occur in the cortex. Stem of a 25 cm-high chamaephyte, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Pachysandra stylosa, transverse section.

Right Fig. 5. Parenchyma unrecognizable. Stem of a 60 cm-high shrub, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Sarcococca hookeriana, transverse section.

pith vrp

Left Fig. 4. Diffuse-porous wood with two rings. The second is very small. Vessel diameter is small (<20 pm). Ray cells have a short radial expansion. Isolated scleren-chyma cells occur in the cortex. Stem of a 25 cm-high chamaephyte, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Pachysandra stylosa, transverse section.

Right Fig. 5. Parenchyma unrecognizable. Stem of a 60 cm-high shrub, cultivated, hill zone, temperate climate, Botanical Garden Zürich, Switzerland. Sarcococca hookeriana, pith transverse section.

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