Wood Anatomy of Crossosomatales: Patterns of Wood Evolution with Relation to Phylogeny and Ecology

The seven families hypothesized by Sosa and Chase to comprise Crossosomatales possess relatively long vessel elements with scalariform perforation plates and scalariform to opposite vessel-ray pitting; tracheids; diffuse axial parenchyma; and heterogeneous rays. These and other primitive character states do not indicate relationships, but they do not offer any evidence against the idea that Crossosomatales are a natural order. Departures from the primitive character states are related to ecological adaptations. Crossosomataceae have simple perforation plates (scalariform briefly at the beginning of the secondary xylem), a feature correlated with the seasonal aridity of habitats occupied by the family, the sole family of the order to exhibit such an ecological shift. Presence of tracheids (which confer embolism resistance to a wood) in ancestors of Crossosomataceae probably pre-adapted the family for entry into highly seasonal habitats. Minimal vessel grouping in all other genera shows that tracheid presence deters vessel grouping; tracheid presence also deters shortening of vessel elements. Autapomorphies are shown by Aphloiaceae (tracheid dimorphism, rays of two distinct widths); Crossosomataceae (perforation plates predominantly simple, lateral wall pitting of vessels alternate); Geissolomataceae (wide rays); Ixerbaceae (fiber-tracheid tendency); Staphyleaceae (adjacence of axial parenchyma to vessels); Stachyuraceae (simplification of perforation plates); and Strasburgeriaceae (large cell size). Although tracheid presence seems plesiomorphic in Crossosomatales, a degree of lability in density and size of bordered pits on imperforate tracheary elements probably occurs within this order and in other dicotyledon groups

Wood Anatomy of Resedaceae

Quantitative and qualitative data are presented for seven species of four genera of Resedaceae. Newly reported for the family are helical striations in vessels, vasicentric and marginal axial parenchyma, procumbent ray cells, and perforated ray cells. Wood features of Resedaceae may be found in one or more of the families of Capparales close to it (Brassicaceae, Capparaceae, Tovariaceae). Lack of borders on pits of imperforate tracheary elements is likely a derived character state. Wood of Reseda is more nearly juvenile than that of the other genera in ray histology; this corresponds to the herbaceousness of Reseda. The quantitative features of wood of Resedaceae are intermediate between those of dicotyledonous annuals and those of dicotyledonous desert shrubs. Wood of Resedaceae appears especially xeromorphic in narrowness of vessels, a fact related to the subdesert habitats of shrubby species and to the dry conditions in which annual or short-lived perennial Resedaceae flower and fruit

Diagonal and Tangential Vessel Aggregations in Wood: Function and Relationship to Vasecentric Tracheids

The list of families with diagonal ( dendritic or flamelike of other authors) patterns of vessel aggregation is similar to the list of families that have vasicentric tracheids. This paper attempts to deal with apparent exceptions. Because of recent reports of vasicentric tracheids, the families with diagonal vessel aggregations are all also on the list of families with vasicentric tracheids with the exception of four families. Genera of those four families are studied to see if a relationship between vasicentric tracheids and diagonal vessel aggregations does hold. Of the families not on both lists, Leitneriaceae (Leitneria), Melastomataceae (Mouriri), and Moraceae (Madura) do prove to have vasicentric tracheids in appreciable numbers. Small numbers of vasicentric tracheids and small degrees of vessel aggregation occur in Asimina (Annonaceae), Morus (Moraceae), and various Araliaceae. Vessels may not appear diagonally grouped if libriform fibers accompanying them are few, or if vessels are separated by large numbers of vasicentric tracheids. Diagonal grouping appears most marked in woods from drier and colder localities. Extensive diagonal vessel aggregations are apparently a reliable indication ofvasicentric tracheid presence, but only a portion of the woods with vasicentric tracheids have diagonal vessel aggregations. By having few, large, and intersecting aggregations of vessels mixed with vasicentric tracheids, a wood has greater potential safety (failure of fewer water columns by air embolisms) in space (within wood) and time than a wood with smaller, more numerous vessel groupings. Vessel grouping and vasicentric tracheid presence are considered additive in their safety effects

Shifting Paradigms in Island Biology

The ease of travel by jet aircraft has opened up island areas not only for study but also for introduction of weeds, pests, and pathogens. We are at a critical juncture in the study of island organisms, which have become more accessible at the same time that they are vanishing. With the urgency for study of island organisms, we have many new tools, especially molecular ones, which have validated the existence of long-distance dispersal in unexpected ways. These tools, together with the ease of staying for longer periods on islands, have permitted us to understand many aspects of evolutionary adaptation on islands: thus, knowledge of biology of island organisms has been accelerated. From the beginning of the age of exploration to the mid twentieth century, there was a preponderant interest in floristics and faunistics of island organisms, but most workers are now concerned with evolutionary and biogeographical studies. Interest in mathematical models of island organisms, originally a pure science concern, is now applied to conservation problems on islands and islandlike mainland areas. Each organism, however, presents unique conservation problems, some perhaps insoluble, and we must place a higher priority on studying native island species while they are still with us in reasonable abundance

Wood and Bark Anatomy of Degeneria

Wood anatomy of the recently described Degeneria roseiflora differs from that of D. vitiensis by possessing narrower vessels, much thicker-walled vessels and fiber-tracheids, abundant uniseriate rays, and greater numbers of ethereal oil cells in rays. Because both large and smaller wood samples of D. vitiensis were studied, ontogenetic changes in the wood are presented and separated from those features that probably vary with the species. Tyloses and perforated ray cells are newly reported for Degeneria. Anatomy of mature bark of D. roseiflora is described. Wood anatomy of Degeneria is moderately primitive. Although Degeneria is often compared to Himantandraceae and Magnoliaceae, Eupomatiaceae also seem very close, if not closer

Wood Anatomy of Caryophyllaceae: Ecological, Habital, Systematic, and Phylogenetic Implications

Wood of Caryophyllaceae is more diverse than has been appreciated. Imperforate tracheary elements may be tracheids, fiber-tracheids, or libriform fibers. Rays may be uniseriate only, multiseriate only, or absent. Roots of some species (and sterns of a few of those same genera) have vascular tissue produced by successive cambia. The diversity in wood anatomy character states shows a range from primitive to specialized so great that origin close to one of the more specialized families of Chenopodiales, such as Chenopodiaceae or Amaranthaceae, is unlikely. Caryophyllaceae probably branched from the ordinal clade near the clade\u27s base, as cladistic evidence suggests. Raylessness and abrupt onset of multiseriate rays may indicate woodiness in the family is secondary. Successive cambia might also be a subsidiary indicator of secondary woodiness in Caryophyllaceae (although not necessarily dicotyledons at large). Although a small shrub, Gymnocarpos may be primitively woody, and because that genus appears primitive in many wood features the family as a whole may derive from woody ancestors, despite apparent secondary woodiness in many phylads. Systematic distribution of wood character states in the family corresponds closely to the Pax and Hoffmann system of three tribes and their progressive degrees of specialization (Paronychieae, Alsineae, Sileneae). Wood data support the idea that Caryophyllaceae represent a branch from near the base of the order Caryophyllales. Wood of Caryophyllaeeae is highly xeromorphic, comparable in quantitative vessel features to wood of desert shrubs; insular species have less xeromorphic wood. Instances of storying and druse presence in axial and ray parenchyma are newly reported for the family, as is the inverted orientation of xylem, phloem, and periderm produced by a cambium at the periphery of the pith in Dianthus caryophyllus

Wood Anatomy of Nolanaceae

Wood of seven collections of six species of Nolana, a genus (18 spp.) of the central western coast of South America was studied for quantitative and qualitative features. The wood is ring porous, with moderately wide vessels bearing simple perforation plates and alternate pits with some grooves interconnecting slitlike pit apertures. Imperforate tracheary elements are fiber-tracheids with vestigial borders on pits or libriform fibers; vasicentric tracheids (reported for Nolanaceae for the first time) are present in varying numbers. Axial parenchyma is vasicentric scanty (sometimes absent), sometimes with tangential bands that may be terminal in part. Rays are both multiseriate and uniseriate; ray cells are mostly erect. Crystal sand occurs in some ray cells and some axial parenchyma. The sum of features mark Nolanaceae as very close to Solanaceae. Wood of Nolana varies in xeromorphy; lower degrees of xeromorphy may be explained by succulence related to maritime habitat or to ephemeral nature of stems. The erect nature of ray cells and a decrease in vessel element length are indicators of paedomorphosis and thereby herbaceous ness of Nolanaceae

Wood Anatomy of Buddlejaceae

Quantitative and qualitative data are presented for 23 species of Buddleja and one species each of Emorya, Nuxia, and Peltanthera. Although crystal distribution is likely a systematic feature of some species of Buddleja, other wood features relate closely to ecology. Features correlated with xeromorphy in Buddleja include strongly marked growth rings (terminating with vascular tracheids), narrower mean vessel diameter, shorter vessel elements, greater vessel density, and helical thickenings in vessels. Old World species of Buddleja cannot be differentiated from New World species on the basis of wood features. Emorya wood is like that of xeromorphic species of Buddleja. Lateral wall vessel pits of Nuxia are small (2.5 ILm) compared to those of Buddleja (mostly 5-7 ILm) . Peltanthera wood features can also be found in Buddleja or Nuxia; Dickison\u27s transfer of Sanango from Buddlejaceae to Gesneriaceae is justified. All wood features of Buddlejaceae can be found in families of subclass Asteridae such as Acanthaceae, Asteraceae, Lamiaceae, Myoporaceae, Scrophulariaceae, and Verbenaceae. Wood anatomy of Buddlejaceae relates to species ecology and size of wood sample, and is not useful in demonstrating that Buddlejaceae are closer to any particular one of these families; such evidence must be sought in molecular data and elsewhere