Amentotaxus Genus (catkin-yew)
6 Species with 3 Trinomials
Amentotaxus as described in 1916, by Robert Knud Friedrich Pilger (1876–1953), in Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie, 54th edition, is commonly known as catkin-yew, a genus of conifers comprising six species. Common names in other languages include 穗花杉属 (sui hua shan shu) in the Chinese language, and Dẻ tùng in Vietnamese. Ament is from the Latin amentum, meaning "thong" or "strap" referring to the male catkins which distinguish this genus from other members of the Taxaceae family.
Although Page (in Kubitzki, Fam. Gen. Vasc. Pl. 1: 299-302. 1990) included it in the Cephalotaxaceae, molecular data indicate very strongly that it is the sister genus of Torreya, which is similar in the size and shape of its seed and in usually having bilaterally symmetric clusters of pollen sacs. Cheng et al. (2000) corroborated this conclusion using chloroplast matK gene analysis, and separately using nuclear data (nrITS sequences).
Description. The catkin-yew species consists of evergreen shrubs or small trees reaching mature heights 7 to 50 feet (2 - 15 m) tall. The species can be either monoecious or dioecious; when monoecious, the male and female cones are often on different branches.
- The leaves are spirally arranged on the shoots, but twisted at the base to lie in two flat ranks (except on erect leading shoots). They are linear-lanceolate shaped, measure 1.6 to 4.8 inches (4 - 12 cm) long and 0.24 to 0.4 inch (6 - 10 mm) broad with soft texture, blunt tips, colored dark green above, and with two conspicuous white stomatal bands below. They differ from the related genus Cephalotaxus in the broader leaves, and from Torreya by the blunt, not spine-tipped leaves.
- The pollen cones (male fruiting bodies) are catkin-like, measuring 1.2 to 6 inches (3 - 15 cm) long, grouped in clusters of 2 to 6 together produced from a single bud.
- The seed cones (female fruiting bodies) are single or grouped a few together on short stems. Seed cones are minute at first, but mature after about 18 months to a drupe-like structure with the single, large nut-like seed that measures 0.6 to 1.2 inches (1.5 - 3 cm) long surrounded by a fleshy covering, colored orange to red at full maturity; the apex of the seed usually protruding slightly from the fleshy covering.
Distribution. The genus is endemic to subtropical southeastern Asia, from Taiwan west across southern China to Assam in the eastern Himalaya, and south to Vietnam.
The genus was present in Europe from the Palaeocene to the Upper Miocene in the form of a single species, which must be referred to as Amentotaxus gladifolia (Ludwig) Ferguson, Jähnichen & Alvin comb. nov. The Tertiary assemblages with Amentotaxus indicate its adaptation to a variety of forest formations. Amentotaxus had a preference for mesophytic forests sometimes with xerophytic elements, subtropical rain‐ and laurel forests and warm‐temperate deciduous woods.