Cephalotaxus, commonly called plum yew or cowtail pine, is a genus of
conifers comprising 11 species, either considered the only member of the family Cephalotaxaceae, or in the
Taxaceae when that family is considered in a broad sense.[1][2] The genus is
endemic to eastern
Asia, though
fossil evidence shows it had a wider
Northern Hemisphere distribution in the past.[1] The species are
evergreenshrubs and small
trees reaching 1.0–10 metres (3–33 ft) (rarely to 20 metres (66 ft)) tall.
Description
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, 4–12 centimetres (1+1⁄2–4+3⁄4 in) long and 3–4 millimetres (1⁄8–5⁄32 in) broad, soft in texture, with a blunt tip; this helps distinguish them from the related genus Torreya, which has spine-tipped leaves.[2]
The species can be either
monoecious or
dioecious; when monoecious, the male and female
cones are often on different branches. The male (
pollen) cones are 5–8 millimetres (13⁄64–5⁄16 in) long, grouped in lines along the underside of a shoot. The female (
seed) cones are single or grouped two to 15 together on short stems; minute at first, they mature in about 18 months to a
drupe-like structure with the single large
nut-like seed 1.5–4 centimetres (5⁄8–1+5⁄8 in) long surrounded by a fleshy covering, green to purple at full maturity. Natural dispersal is thought to be aided by
squirrels which bury the seeds for a winter food source; any seeds left uneaten are then able to germinate.[2]
Phytochemistry
Cephalotaxus species produce
cephalotaxine, an
alkaloid. Parry et al 1980 provides evidence that cephalotaxine is a
phenylethylisoquinoline. However, they also find this genus to be unable to incorporate
cinnamic acid into cephalotaxine, and incorporation of cinnamic acid is usually a step in phenylethylisoquinoline syntheses, throwing the phenylethylisoquinoline theory in to question.[3]
Phylogeny
Molecular studies place Cephalotaxus as the most basal member of the
Taxaceae, having a very ancient divergence from them during the late
Triassic.[4] Historically, it was placed as the only member of the family Cephalotaxaceae, due to strong morphological differences from other members of Taxaceae,[5] but major authorities consider the family synonymous with Taxaceae.[6][7]
Extant species
The taxonomy of Cephalotaxus is difficult, because the species have been defined using characteristics that intergrade with each other, such as the length and shape of needles, bark, and stomatal band color. Cephalotaxus species have often been separated geographically rather than morphologically.[8]
The oldest fossils of Cephalotaxus are known from the
Eocene of
Heilongjiang in northeast China and the
Messel Pit of Germany. The youngest fossils of Cephalotaxus in Europe date to the
Pliocene, and remains are also known from the
Miocene of western North America.[11][12]