Most massive = Giant Sequoias Sequoiadendron giganteum (Cupressaceae) ... The conifers have the ..The Tallest = Coastal Redwood (Sequoia sempervirens) (Cupressaceae) . .. And the oldest = Bristlecone Pine Pinus longaeva (Pinaceae). Welwitschia mirabilis Welwitschiaceae young plant Note 2 strap-like leaves As Welwitschia grows the 2 leaves split into many sections. Welwitschia is dioecious with separate male and female plants. Plant with female cones Plant with male cones Welwitschia mirabilis can live for up to 2000 years by which time the two leaves have shredded into multiple straps. ttp://www.cactusandsucculent.org/riviste/2000/fascicolo-4/foto/welwitschia-mirabilis.jpg Courtesy of Amy Dieckmann 05 Escalante National Monument, Ephedra in the foreground Ephedra Plant Female strobilus (cone) Male strobili (cones) From Tree of Life Web Site, U. of AZ Gnetum, a woody plant with vessels a. Longitudinal tracheid of pine. b. Vessel of a hardwood (early wood) c. Vessel of a hardwood (late wood) e. Trachied of a hardwood. c. Hardwood fiber cell (provides support) Gnetophytes and Angiosperms have vessels. Anthophyte Hypothesis Gnetifer Hypothesis Two trees illustrating the Anthophyte vs Gnetifer Hypotheses Anthophytes Gnetifers (Extinct)