Characteristics of the xylem

In the present material annual rings are absent or indistinct (Fig. 1). Vessels are solitary or in the majority of cases arranged in short radial multiples or groups (2-4 vessels; Figs. 2-4). Ear-lywood vessel diameter varies between 40-140 pm. Especially lianas have large vessels (Bougainvillea, Commicarpus; Figs. 1 and 3). Vessels contain exclusively simple perforations. Inter-vessel pits are in the majority of cases small and round, but are sometimes partially slit-like or can be scalariform (Abronia latifolia; Fig. 5). Vestured pits are clearly visible with the light microscope on material stained only with safranin. Dark-staining substances occur in the center of the stem of Bougainvillea and large v f small , v

Commicarpus. The radial walls of fibers of all species are perforated by very small slit-like or round pits (<2 pm). Fibers can be thin- or thin- to thick-walled or are absent in the prostrate Abronia latifolia (Fig. 3). Paratracheal parenchyma occurs in 3 species and pervasive parenchyma is characteristic of Abronia latifolia (Fig. 3). Rays are absent in Commicarpus boissieri and 4 species have rays with 1-4 cells. All species contain lateral cambia which produce open vascular bundles arranged in more-or-less distinct concentric bands (Figs. 1-4). Rays are absent within vascular-bundles. The conjunctive tissue is storied, except in Abronia fragrans, and thin-walled (Figs. 1-4). Medullary vascular bundles (Figs. 6 and 7) and rhaphides in idioblasts (Figs. 8 and 9) were found in all species analyzed.

Fig. 2. More-or-less concentrically arranged vascular bundles. Some vascular bundles stay solitary, but some are linked with a continuous fiber band and conjunctive tissue. Vessels stand in radial multiples. Long prostrate hemicryptophyte, embedded in sand, cold steppe, Great Sand Dunes, Colorado, USA. Abronia fragrans, transverse section.

Fig. 1. Concentrically arranged vascular bundles are surrounded by thin-walled conjunctive tissue (parenchyma) and thin- to thick-walled fibers. Characteristic of the liana is the presence of large and small vessels. The two growth ring boundaries are barely discernible. Liana on a wall, cultivated, subtropical climate, Mt. Isa, Australia. Bougain-villea spectabilis, transverse section.

Fig. 2. More-or-less concentrically arranged vascular bundles. Some vascular bundles stay solitary, but some are linked with a continuous fiber band and conjunctive tissue. Vessels stand in radial multiples. Long prostrate hemicryptophyte, embedded in sand, cold steppe, Great Sand Dunes, Colorado, USA. Abronia fragrans, transverse section.

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Fig. 3. Single vascular bundles are surrounded by thin-walled, unlignified conjunctive parenchyma. The parenchyma between the vessels is ray-like. Vessels are surrounded by pervasive parenchyma. Fibers are missing. Only the vessel walls are lignified. Long prostrate hemicryptophyte, embedded in sand, coast-line, Astoria, Oregon, USA. Abronia latifolia, transverse section.

Fig. 1. Concentrically arranged vascular bundles are surrounded by thin-walled conjunctive tissue (parenchyma) and thin- to thick-walled fibers. Characteristic of the liana is the presence of large and small vessels. The two growth ring boundaries are barely discernible. Liana on a wall, cultivated, subtropical climate, Mt. Isa, Australia. Bougain-villea spectabilis, transverse section.

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Left Fig. 4. More-or-less concentrically arranged vascular bundles. The vascular bundles are linked by a continuous fiber band and a thin-walled unlignified conjunctive tissue (parenchyma). 4 m-long prostrate liana, sea shore, subtropical climate, Dho-far, Oman. Commicarpus boissieri, transverse section.

Right Fig. 5. Scalariform inter-vessel pitting. Only the vessel walls are lignified. Long prostrate hemicryptophyte, embedded in sand, coast-line, Astoria, Oregon, USA. Abronia latifolia, transverse section.

raphides in idioblasts

■J Left Fig. 6. Vascular bundles in the pith (medullary vascular bundles). Liana on a wall, cultivated, subtropical climate, Mt. Isa, Australia. Bougainvillea spectabilis, transverse section.

Right Fig. 7. Vascular bundles in the pith of an annual shoot (medullary vascular bundles). Long prostrate hemicryptophyte, embedded in sand, cold steppe, Great Sand Dunes, Colorado, USA. Abronia fragrans, transverse section.

raphides in idioblasts

Left Fig. 8. Rhaphides in parenchyma cells of the xlylem. Liana on a wall, cultivated, subtropical climate, Mt. Isa, Australia. Bou-

gainvillea spectabilis, radial section, polarized light.

Right Fig. 9. Rhaphides in idioblasts (black dots) in the thin-walled conjunctive parenchyma. 4 m-long prostrate liana, seashore, subtropical climate, Dhofar, Oman.

Commicarpus boissieri, radial section.

Characteristics of the phloem and the cortex

Ecological trends in the phloem and the pith

The anatomy of the bark of all species is characterized by the absence of sieve tubes, the presence of parenchyma cells in different sizes and the presence of rhaphides (Figs. 10 and 11).

There is not sufficient material to identify any ecological trends or characteristic features of species.

Left Fig. 10. Simple construction of the phloem and the cortex. Dilatation expands the cortex cells from the cambium to the periphery. Long prostrate hemicryptophyte, embedded in sand, cold steppe, Great Sand Dunes, Colorado, USA. Abronia fragrans, transverse section.

Right Fig. 11. Simple construction of the phloem and the cortex. The parenchyma stays in regular radial rows. 4 m-long prostrate liana, seashore, subtropical climate, Dhofar, Oman. Commicarpus boissieri, transverse section.

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