Cephalotaxus fortunei (Cephalotaxaceae
) was included on the basis that homoharringtonine, an alkaloid isolated from a related species, Cephalotaxus harringtonia, is undergoing clinical trials against leukemia (Cragg et al.
Group 2 Conifers: Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae
Four modern taxa representing the Araucariaceae, Cephalotaxaceae, Pinaceae, and Podocarpaceae were analyzed by the exhaustive search option with the Majonicaceae, using Ernestiodendron and Moyliostrobus together as the outgroup.
Florin (1951) and Schweitzer (1963) thought that the Cephalotaxaceae evolved from ancestors more like Ernestiodendron than Utrechtia (formerly Lebachia), because the ovuliferous scale in Cephalotaxus seems to consist of fertile elements only.
Modem work on conifer phylogeny shows no close agreement on a hypothesis of relationships of the Cephalotaxaceae. Hart's (1987) cladistic analysis shows this family as a sister group with the Taxaceae in his shortest trees.
My 1988 study links the Podocarpaceae and Cephalotaxaceae, but there is no agreement with other work, including the present results.
Other studies that include Hirmeriella place the latter at the base of a group that includes the Pinaceae and Araucariaceae (Miller, 1982: [ILLUSTRATION FOR FIGURE 4 OMITTED]), at the base of a group including all modern families except the Cephalotaxaceae (Miller, 1982: [ILLUSTRATION FOR FIGURE 3 OMITTED]), and at the base of a subclade involving the Cephalotaxaceae and the Podocarpaceae.
The Taxaceae are distinguished from other conifer families (except for Cephalotaxaceae) by compound pollen strobili or simple structures derived from compound pollen strobili, peltate microsporophylls, and solitary, terminal ovules embedded in a fleshy closed or open aril.
Hart's (1987) preliminary cladistic analysis supports this theory and positions the Cephalotaxaceae and the Taxaceae as sister groups.
Amentotaxus has been allied with Cephalotaxus as a member of the Cephalotaxaceae, the sister family and best outgroup to the Taxaceae (Hart, 1987; Keng, 1969).
The microsporangia are dorsiventral, but occasionally radial symmetry is displayed, at least near the strobilus apex, a condition also observed in the Cephalotaxaceae (Wilde, 1975).
Foliar resin is present in the leaves and arils as in Torreya and the Cephalotaxaceae, although Amentotaxus is the only genus of the Taxaceae that has its resin organized into a duct or canal (Ferguson, 1978; Jeffrey, 1903; Keng, 1969; Singh, 1961).