Abstract:

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.