WOOD ANATOMY OF SYMPETALOUS DICOTYLEDON FAMILIES - A SUMMARY, WITH COMMENTS ON SYSTEMATIC RELATIONSHIPS AND EVOLUTION OF THE WOODY HABIT

Data on wood anatomy are presented in tabular form for 56 sympetalous families of dicotyledons arranged according to the system of Dahlgren, who was influenced by data from presence or absence of iridoids and by embryological information. Each order is reviewed in terms of the degree of correlation of wood data with data from chemistry and embryology. Original data are presented for Buddlejaceae, Globulariaceae, and Selaginaceae. Ericales prove to be a natural and rather primitive group. Cornales as a whole are primitive, but Adoxaceae and Stylidiaceae have distinctively specialized woods. Dipsacales are highly diverse on the basis of woods, creating interpretational questions. Gentianales are a natural group on the basis of wood and of intraxylary phloem in primary stems; Oleales and Rubiales are peripheral to Gentianales. Scrophulariales and Lamiales have specialized wood and are probably natural groupings, but there is no difference between the orders on the basis of wood anatomy. Recognition of particular families within Scrophulariales and Lamiales is aided by wood anatomy: Buddlejaceae, Globulariaceae, and Selaginaceae are distinctive families in Scrophulariales; Avicenniaceae, Chloanthaceae, and Stilbaceae (the last of which should include Retziaceae) should be recognized in Lamiales. Wood anatomy does not aid in differentiating Solanales from Boraginales. Wood of Asterales is rather uniform in characters of major evolutionary significance, despite its diversity in ecological wood anatomy. Lamiales and Scrophulariales have wood similar to that of Asteraceae, but so do Apiaceae, which share chemical features with Asteraceae, Campanulales, and some Dipsacales. Among families incertae sedis, Desfontainiaceae (often relegated to Loganiaceae) should be recognized under Cornales near Escalloniaceae, as should Columelliaceae. Fouquieriaceae bear resemblances to Cornales and Ericales, but deserve isolation in a monofamilial order. Familial assignment of the genera Leucophyllum, Oftia, and Paulownia is discussed.