The compound pollen strobilus in Amentotaxus and Austrotaxus easily distinguishes these genera from all other conifers.
Resin is organized into a canal in the leaves of Amentotaxus (Keng, 1969), appears in scattered cells in the foliar parenchyma of Torreya, is found only in the roots and wounded stems of Taxus (Bliss, 1918), and is lacking in Pseudotaxus and Austrotaxus.
Leaves spirally arranged; pollen strobili axillary; tracheids lacking spiral thickenings Austrotaxus 1.
Amentotaxus is easily distinguished from Austrotaxus by its opposite leaves and from all other genera in the family by its terminal racemes of pollen strobili.
The compound pollen strobili of Austrotaxus have a unique arrangement whereby the stalks of the microsporophylls are vestigial, the microsporangia of each microsporophyll are fused to each other and partially adnate to the microsporophyll itself (Saxton, 1934; Wilde, 1975).
Austrotaxus may also be distinguished by its apparent lack of spiral thickenings on the tracheid walls that is so distinctive of Taxaceae wood (Greguss, 1955).
Austrotaxus is not cultivated to any extent in this country.
Taxus differs from Torreya in its obviously alternate leaves and open red aril; from Pseudotaxus by its red aril, lack of sterile scales among the microsporophylls, and fewer scales subtending the ovule; from Austrotaxus by its simple pollen strobili and smaller leaves; and from Amentotaxus by its alternate leaves and simple, axillary pollen strobili.
The leaves of Taxus are distinctive because of the expanded, papillose subsidiary cells of stomata being amphicyclic as in Austrotaxus and resin canals lacking as in Pseudotaxus and Austrotaxus (Florin, 1948c).
The anti-cancer agent, taxol, present in Taxus and Austrotaxus, has not been identified in Torreya.