Coniferales

 

Cephalotaxaceae

 

The taxonomic position of this family of conifers has been much confused during recent years as it shows many affinities with the Yews (Taxaceae) - which it resembles morphologically - but because of the very distinct seed and fruit formation it has for long been retained as a separate entity in the Coniferales – but now that the Taxaceae are accepted as conifers many authorities suggest it should be merged with the Taxaceae. It is in this early part of the evolution of this branch of the Coniferales that the relevant DNA analysis and assessment does not yet seem to have resolved all the relationships fully. However from the point of view of the propagator, because the seed production is distinct it is more relevant to treat it separately.

 

This family consists of the single genus Cephalotaxus (although some authorities include Amentotaxus in this family and yet others include Torreya). The genus is also ill-defined insofar as there is disagreement as to which taxa are constituted as species and which are delegated as variants – at the most diverse interpretation eleven species are recognised. As in Taxus there is a school of thought which includes all the relevant ‘hardy’ species from the Asiatic mainland (C. fortunei, C. harringtonia, C. koreana and C. sinensis) in one catch-all species. These species are then recognised as geoclimatic variants. The propagator however will pick a name and verify as far as is possible that the seed sample represents the provenance and entity desired.

 

The genus Cephalotaxus consists of evergreen, densely foliaged, much branched, small trees and shrubs which are found in Eastern Asia – the hardier species occur chiefly in China, Korea and Japan. The plants are to all intents and purposes dioecious.

 

The male cones shed their pollen in the early spring and pollination is by wind. The female cones are found on the newest shoots - one to three together and the cones and seeds take two years to mature. The cone consists of one to a few ovuliferous scales with each scale carrying two seeds – only one of which matures. As the fruit matures the scale develops into a fleshy, often colourful, aril which surrounds the seed and encloses it. Thus the fruit consists of a stem with a few ‘olive looking’ drupe-like seeds. The drupes are 2-3cm long and are taken by birds and mammals. The seed itself is acorn shaped and is surrounded by a hard seed coat which protects it in the passage through the gut.

 

At dispersal the embryo is immature and the imbibed seed requires a period of warn stratification to mature the embryo. The same practical procedures to achieve a successful germination, as are recommended for the Taxaceae, should be applied. The seedling has two cotyledons.

 

The seeds are big enough to be handled individually and can, consequently, be sown in individual containers if so required. A speedy germination will be achieved at 18-20˚C.

 

Eventually the seedlings of all the relevant species need to develop a mycorrhizal association in order to achieve optimal growth. The relevant fungi are of the vesicular-arbuscular type. This relationship should therefore be accounted for during the production process.

 

As these plants grow as understorey plants in open forest they are adapted to shade and humid conditions consequently they are unsuited to arid conditions or to exposure to full sun.