| 词条 | Cephalotaxaceae |
| 释义 |
| image = Cephalotaxus_harringtonia_BotGardBln1105WithSeeds.JPG | image_caption = Cephalotaxus harringtonii | taxon = Cephalotaxaceae | authority = Neger | subdivision_ranks = Genera | subdivision =Amentotaxus Cephalotaxus Torreya }} Cephalotaxaceae is a small grouping of conifers, with three genera and about 20 species, closely allied to the Taxaceae, and included in that family by some botanists. They are restricted to east Asia, except for two species of Torreya found in the southwest and southeast of the United States; fossil evidence shows a much wider prehistorical Northern Hemisphere distribution. The differences between Taxaceae and Cephalotaxaceae are notable in the cone aril, which fully encloses the seeds of Cephalotaxaceae, the longer maturation of Cephalotaxaceae seeds and the larger size of the mature seeds. These are much branched, small trees and shrubs. The leaves are evergreen, spirally arranged, often twisted at the base to appear biranked. They are linear to lanceolate, and have pale green or white stomatal bands on the undersides. The plants are monoecious, subdioecious, or dioecious. The male cones are 4–25 mm long, and shed pollen in the early spring. The female cones are reduced, with one to a few ovuliferous scales, and one seed on each ovuliferous scale. As the seed matures, the ovuliferous scale develops into a fleshy aril fully enclosing the seed. The mature aril is thin, green, purple or red, soft and resinous. Each ovuliferous scale remains discrete, so the cone develops into a short stem with one to a few berry-like seeds. They are probably eaten by birds or other animals which then disperse the hard seed undamaged in their droppings, but seed dispersal mechanisms in the family are not yet well researched. External links
2 : Pinales families|Cephalotaxaceae |
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