XI. On Asterochlænopsis, a new genus of zygopterid tree-ferns from Western Siberia

Abstract

About fifty years ago a Swedish, engineer picked up a silicified stem near Semipalatinsk, in the Kirgis Steppes in Western Siberia. The fossil was cut transversely into several slabs, at least five of which ultimately found their way to Germany. One of the pieces reached the hands of K. G. Stenzel of Breslau and he described it in 1889 under the name Asterochloena (Clepsydropsis) kirgisica . Another fragment came into the hands of A. Schenk, then professor of botany at Leipzig, and apparently in ignorance of Stenzel’s fossil, he described it in the same year under a distinct name, Rachiopteris ludwigii Leuckart and Schenk. The ultimate sources of the two specimens are so nearly identical that the present writer, in a paper published in 1919, suggested that they were probably pieces of one and the same stem. This suspicion was recently confirmed in an indirect way by Prof. Karl Wanderer of Dresden (see below), and since then all doubt on the matter has been removed by a direct comparison of the two type-specimens, which have been found to fit against each other. Besides these two fragments it has been possible, during a recent tour in Europe, to relate to the same original stem three other pieces, one of which was preserved in Dresden, one in Chemnitz and the third in Breslau. The Breslau fragment, originally in the possession of Goeppert, was mentioned by Stenzel in his memoir, already cited above ; the other two specimens do not appear to have been noticed in the literature (see text-fig. 1).