Taxaceae, the yew family, is a family of coniferous trees and shrubs which includes six extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species.
Description
They are many-branched, small trees and shrubs. The leaves are spirally arranged, often twisted at the base to appear 2-ranked. They are linear to lanceolate, and have pale green or white stomatal bands on the undersides.
The plants are dioecious, or rarely monoecious. The catkin like male cones are 2–5 millimetres (0.079–0.197 in) long, and shed pollen in the early spring. They are sometimes externally only slightly differentiated from the branches. The fertile bracts have 2-8 pollen sacs.
The female 'cones' are highly reduced. Only the upper or uppermost bracts are fertile and bear one or rarely two seeds. They may be found on the ends of branches or on the branches. They may grow singly or in groups or clumps.
As the seed matures, a fleshy aril partly (Amentotaxus, Austrotaxus, Pseudotaxus, Taxus) or fully (Cephalotaxus, Torreya) encloses it. The developmental origin of the aril is unclear, but it may represent a fused pair of swollen leaves. The seeds in some genera are highly poisonous, containing the poisons taxine and taxol, but the mature aril that surrounds them is soft and juicy, often brightly coloured and sweet, but resinous-flavoured in others; it is eaten by birds which then disperse the hard seed undamaged in their droppings. However, if damaged the seeds could release their poisons, which is dangerous for humans.
Distribution
Species are mostly found in the tropics and temperate zones in the northern temperate. There are only a few species in the southern hemisphere.
Classification
Taxaceae is now generally included with all other conifers in the order Pinales, as DNA analysis has shown that the yews are phylogenetically nested in the Pinales, a conclusion supported by micromorphology studies. Formerly they were often...
