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Wood of Bruniaceae is very primitive according to widelyaccepted criteria. Vessels are relatively long, with scalariform perforation plates having numerous bars, fully or vestigially bordered. Many aberrations in disposition of bars and perforations in perforation plates are present, and no species has exclusively normal perforation plates. Lateral wall pitting of vessels, both intervascular and between vessels and rays, is scalariform to opposite. Vessels are solitary or nearly so, angular to round in transection. Helical thickenings are present in vessels of only a single species. All imperforate elements are thick-walled tracheids, some with gelatinous walls. Tracheids are only slightly longer (in two instances shorter) than the vessel elements they accompany in any given species. Axial parenchyma is diffuse, with very slight tendencies toward aggregates or vasicentric scanty. Rays are heterocellular, with a predominance of upright cells, or upright cells exclusively in species with very narrow multiseriate rays. Multiseriate rays vary from biseriate to an average of more than five cells in width, according to species. Uniseriate wings are present on at least some multiseriate rays in all species. Borders are frequently present on the tangential walls of ray cells, which tend to be thick. U niseriate and multiseriate rays are present in all species. Growth rings vary from absent to conspicuous, the latter mostly in montane species. Inconspicuous growth rings feature narrow vessels or narrow tracheids in latewood. More pronounced growth rings have more numerous as well as wider vessels in earlywood; vessels may be absent or nearly so in latewood, which would thus constitute an all-tracheid band produced annually. Crystals are present in rays of most species, sometimes chambered in subdivided ray cells. A few species have crystals in chambered axial parenchyma cells. Droplets or massive deposits of amorphous dark-staining compounds are present in all species. Woods of Bruniaceae are exemplary, considering their primitiveness, for adaptation to xeromorphy, based on current concepts of wood xeromorphy. Vessels are notably narrow or numerous per mm2 of transection, or both. The nature of growth rings and of perforation plate modifications are suggestive of xeromorphy. Although species of moister habitats do have quantitatively more mesomorphic wood features, the span within Bruniaceae is not great, suggesting that wood of the family as a whole is adapted to extremes of water stress in accordance with the dry, hot summers, high incidence of wind, and porous sandstone soils of Cape Province, South Africa. Lignotubers have woods more parenchymatous and mesomorphic than wood of stems in the lignotuber- bearing species. Wood of stems does not differ appreciably from that of roots. Bruniaceous woods are most closely comparable to those of Geissolomataceae and Grubbiaceae, although other "rosoid" families have similar woods. This agrees with the "rosoid" placement accorded Bruniaceae by most phylogenists.

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© 1978 Sherwin Carlquist

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