CHAP, v Palaeobotany, 1860-1900 143 



Arthropitys or Calamites proper, and Calamodendron. 

 The latter included the forms originally considered Gymno- 

 sperms by Brongniart. The affinities of the Calamites with 

 the Equisetaceae were not clearly established till nearly 

 the end of the century. 



Our knowledge of Sphenophyllum dates from Renault's 

 work of 1870, if we except a reference to its anatomy 

 made by Dawson four years earlier. Though Renault 

 communicated his paper to the French Academy in 1870 

 the full publication did not appear till 1873. In 1874 

 Williamson described two other species which he then 

 called Asterophyllites sphenophylloides a.ndA.insignis, both 

 of which were subsequently recognized as true Spheno- 

 phylla. The first showed certain points of difference 

 from some of Renault's specimens, particularly in the 

 arrangements of the protoxylem groups. Both species were 

 more fully investigated by Williamson and Scott in 1893. 



The fructification of this plant was known for several 

 years before its relationships were ascertained. The first 

 description of it was given by Binney in 1870, under 

 the name of Bowmanites cambrensis. In the next year 

 Williamson described another specimen, which he named 

 Volkmannia Dawsoni, a fuller account of which he 

 published in 1873. In 1884 Weiss showed them both to 

 belong to a single genus, and Binney's name having priority, 

 Williamson's fossil was named Bowmanites Dawsoni. 

 Under this name he published a very complete description 

 of its organization and structure in two memoirs dated 

 1890 and 1891. Two years later Zeiller gave to the Geo- 

 logical Society of France a very detailed account of the 

 structure of some very finely preserved strobili of Spheno- 

 phyllum from the French and Belgian coal-measures, and 

 showed that they agreed in every essential particular 

 with Williamson's fossils. His conclusions were accepted 

 by the latter, and the strobilus received its final name, 



