X. Miadesmia membranacea , Bertand; a new Palœozoic Lycopod with a seed-like structure

Abstract

Professor Bertrand’s account of this interesting little Lycopod (“Sur une nouvelle Centradesmide,” Assoc. Franc. pour l’Avancement des Sciences, 1894), is based on English material. He found fragments of leaves and twigs, associated with those of Lepidodendron Harcourtii , in preparations from the nodules of the Gannister beds at Hough Hill, sent him by Mr. Lomax. In describing these for the first time, he gave them the name of Miadesmia membranacea . The leaves bear a large ligule of a definite form and characteristic structure and insertion. They are provided also with a thin margin. This feature is noted by Professor Bertrand as exceedingly useful in the diagnosis of Miadesmia. The sporophylls have only recently been obtained, and it is with these the present paper is chiefly concerned. The megasporophylls were first recognised by Dr. Scott in a series of sections passing tangentially through a single large Lepidocarpon megasporophyll. These new structures proved to be exceptionally interesting, on account of their advanced seed-like character. Not only are the sporangia equipped with an integument and physiological stigma, but the single megaspore is retained in the sporange and resembles the embryo-sac of a Phanerogam in a very marked degree. I simultaneously received from Mr. Lomax a number of excellent preparations, and it is due to him to record that he recognised the seed-like nature of the new bodies. An investigation of older preparations in the R. H. C. Collection revealed several microsporophylls and foliage leaves of Miadesmia. Professor Weiss, moreover, has kindly lent from the Manchester Collection several slides which are rich in Miadesmia. Dr. Scott has contributed not only a large number of invaluable preparations, but has helped most fundamentally in all the more difficult problems connected with the work. To Dr. Scott, then, I offer my best thanks, and also to Professors Oliver and Weiss.