The Bakerian lecture—On the organization of the fossil plants of the coal-measures.—Part IX. On the latest researches into the organization of the fossil plants of the British coal-measures, especially of the calamites and lepidodendra

Abstract

The first plant noticed is one of which a transverse section was figured in the lecturer’s Memoir, Part I., under the belief that it was Calamitean. It now proves not to be so, but is a branching non-articulated plant, lacking the nodes and the longitudinal internodal canals so characteristic of the Calamites. It has a large parenchymatous medulla with radiating prolongations separating the very distinctly defined wedges of the vascular zone. From the peculiar shape thus given to transverse sections of the medulla the author has assigned to the plant the provisional name of Astromyelon . In the place of the canal of Calamites the thin medullary extremity of each vascular wedge is occupied by a few larger and often more conspicuous vessels than those forming the rest of the wedge. The medulla farther differs from that of Calamites in being rarely fistular. Each wedge consists of a series of regular radiating laminæ of barred vessels separated by numerous medullary rays—the latter varying in composition from a solitary cell to numerous cells arranged in single vertical series. Nearly all the stems and branches of this plant are found to be decorticated. One specimen found by Mr. Butterworth is surrounded by a very thin cortex consisting only of three or four layers of parenchymatous cells. Astromyelon forms another example of the numerous carboniferous plants whose vascular zone grew by exogenous additions, yet the exclusion of every modification of tissue, except barred vessels, from the vascular laminæ suggests Cryptogamic rathter than Gymnospermous aflinities. Astromyelon is the only distinct type of plant left undescribed in the lecturer’s previous Memoirs; but he has obtained a considerable amount of additional information respecting some of those previously examined.