The abundance of Coniferae in Szechuan Province is a well-known fact, especially
of the Order Pinales. There are so far 19 genera 68 species and varieties belonging to
the Pinaceae, Taxodiaceae and Cupressaceae. This paper dealing with the fundamental
features in the distribution of these plant-groups may be not only of scientific inte-
rest but also of great importance to forestry.
According to an analysis of the influence of historic, geographic and ecological con-
ditions on the distribution of plants, it is shown that the differantiation of geographical
distribution of genera and species in these 3 familias between the eastern and
the western areas is very evident. There are (Tab. 1) 18 genera and 27 species in the
eastern area, including 6 monotypic genera, they are Cathaya, Pseudolarix, Metosequoia,
Glyptostrobus, Fokienia and Platycladus. As the great concentration of the monotypic
and paleo-endemic genera is not found elsewhere, this area therefore distinctly indicates
the relic nature. It seems most probably that they came originally into existence in sub-
tropical and warm-temperate climates of middle lalitudes in the northern hemisphere,
and most of them are in the lands bordering the Pacific Ocean.
On the other hand, there are 13 genera and 56 species in the western area with
only one monotypic genus (Platycladus) present, and most genera are polytypic with
wide ranges. The number of species in these genera here is larger than in any other
areas, for example, Abies and Picea are represented 12 species each (Fig. 1-4). There
are 10 species in Sabina (Fig. 5). It might be considered that each genus has develop-
ed into a great centre, In addition, it has been discussed in detail regarding the
vicarious distributions in geography, verticality, and ecology of ralated species in Abies,
Picea, Tsuga, Keteleeria, Larix, Pinus and Cupressus (Fig. 3-5), as well as the re-
lationship of these species. As shown above, these plants are also, without doubt, of
very old origin. Moreover, they are most likely very much closely related with Tethys
in the past, but the majority species apparently have arisen in relalively recent times.
They are due to the effect of mountain-making and glaciation, principally in
consequence of the cooling process of the climatic vicissitude.
