268 



Prof. Williamson on the Organization of the [Jan. 26, 



composed of a single mineral species varying in colour, is proved by the 

 analytical results given in this memoir. It has been found to be a bronzite 

 of the formula (Mg^ Fe^ ) Si 3 , and in association with it there occurs 

 some chromite in distinct crystals. 



Rammelsberg has also recently published the results of an examination 

 of this meteorite (Pogg. Annalen, vol. cxlii. p. 275), and finds in it a 

 bronzite associated with 12 per cent, of olivine. It is probable that the 

 meteorite varies in its composition in different parts, and that Prof. Ram- 

 melsberg analyzed that portion where an olivinous ingredient was in ap- 

 preciable preponderance. 



The mottled kind was treated with hydrogen chloride in the cold, and 

 subsequently with potash, and again with hydrogen sulphate and potash, 

 but in each case it was noticed that the action of the acid was confined to 

 that of a solvent. A little meteoric iron was dissolved, but no appreciable 

 amount of olivine was found in the portion examined in the Laboratory at 

 the British Museum. 



II. " On the Organization of the Catamites of the Coal-measures." 

 By W. C. Williamson, F.R.S., Professor of Natural History in 

 Owens College, Manchester. Received November 11, 1870. 



(Abstract.) 



Ever since M. Brongniart established his genus Calamodendron, there 

 has prevailed widely a belief that two classes of objects had previously 

 been included under the name of Catamites — the one a thin -walled Equise- 

 taceous plant, the Catamites proper, and the other a hard-wooded Gymno- 

 spermous Exogen, known as Calamodendron. This distinction the author 

 rejects as having no existence, the thick- and thin-walled examples having 

 precisely the same typical structure. This consists of a central pith, sur- 

 rounded by a woody zone, containing a circle of woody wedges, and enclosed 

 within a bark of cellular parenchyma. 



The Pith has been solid in the first instance, but very soon became 

 fistular, except at the nodes, at each one of which a thin diaphragm of 

 parenchyma extended right across the medullary cavity. Eventually the 

 pith underwent a complete absorption, thus enlarging the fistular interior 

 until it became coextensive with the inner surface of the ligneous zone. 



The Woody Zone. — This commenced in very young states by the 

 formation of a circle of canals stretching longitudinally from one node to 

 the adjoining one. Externally to, but in contact with, these canals a few 

 barred or reticulated vessels were found ; successive additions to these were 

 made in lines radiating from within outwards ; hence each wedge consisted 

 of a series of radiating laminae, separated by medullary rays, having a 

 peculiar mural structure. At their commencement these wedges were 

 separated by wide cellular areas, running continuously from node to node ; 



