Recent experimental studies on the hydraulic functioning of a range of extant woody plants have demonstrated trade-offs between vessel diameter, vessel density and total vessel length. Hydraulic architecture can be classified into five extreme types: 1) long, wide diameter vessels in high density (prevalent in modern lianas); 2) long, wide diameter vessels in low density (prevalent in modern lowland tropical rainforest trees); 3) short, narrow diameter vessels in high density (prevalent in modern temperate diffuse-porous woods, especially in desert shrubs); 4) a combination of long, wide earlywood vessels and numerous, narrow and short latewood vessels (in modern ring-porous woods of temperate and subtropical regions); 5) a combination of long, relatively wide vessels and narrow, short vessels mixed throughout the wood (in a number modern lianas and xeric woody species). The first appearance of these 5 wood types in the fossil record (1500+ records reviewed) and their incidence over time will be briefly reviewed and related to environmental changes, as will the wood anatomy of selected families, e.g., Fagaceae, Juglandaceae, Lauraceae, Ulmaceae.

Key words: Juglandaceae, Lauraceae, paleobotany, secondary xylem, Ulmaceae, wood