一种木化石Phoroxglon scalariforme Sze的构造及其亲缘关系

ON THE STRUCTURE AND RELATIONSHIP OF PHOROXYLON SCALARIFORME SZE

1951年本文作者曾描述采自北满鸡西县之城子河的一种奇异的木化石,因其次生木质部的构造的特殊,作者当时曾为此种木化石创立一新的属名Phoroxy-lon。1953年秦鼐同志复在热河瓦房子矿山小西山山脊最西的山头白垩纪地层中采得同样木化石。热河的标本共直经宽约15厘米,全系次生木质都所组成(本文图版Ⅰ,图1)。视其外表形态确和松柏类的木化石毫无异致。

The purpose of this paper is to place on record a fossil wood recentlyfound from the supposed Cretaceous beds of the Jehol province,N.China.The specimen is found to be identical with the remarkable species Phoroxylonscalariforme described by Sze in 1951 of Northern Manchuria.As far as thefeatures of the secondary wood alone are concerned,the Chinese species mightprobably be more nearly allied to the two species of Bucklandia:B.sahniiBose and B.indica Seward.It recalls B.sahnii in regarding to the overwhel-ming scalariform pittings on the radial walls of the tracheids,although thepronounced uniseriate and multiseriate rounded bordered pits of the latter speciesare still not to be observed.The species resembles also B.indica in regardingto the uniseriate structure of the medullary rays as seen in the tangential sections,but the latter species is distinguished by its thoroughly multiseriate borderedpits on the radial walls of the tracheids.Furthermore,the stems of the twoIndia species,like many other species of Bucklandia are characterized by arather wide pith in central portion.The wood found from Jehol is measuredmore than 15 cm in diameter and is composed nearly entirely of the secondarywood.This difference does appear to be of sufficient importance for at least gene-ric separation.Since only the secondary wood is available,many of the ana-tomical features of P.scalariforme is unknown.It appears that the evidence ofrelationships of the Chinese species hardly amounts to proof that it belongs alsoto the Bennettitales.The former conjecture of the present writer that thisspecies might probably belong to one of those extinct Mesozoic conifers couldhowever,probably be ruled out.The English version of the present paper will appear in concurrent issue ofActa Scientia Sinica,Vol.Ⅲ,No.4,