158 Mr. Thomas Hick on 



On the primary structure of The Stem of Calamites. 

 By Thomas Hick, B.A., B.Sc, Assistant Lecturer 

 in Botany, Owens College, Manchester. Communi- 

 cated by F. E. Weiss, B.Sc, Professor of Botany 

 in the Owens College. 



(Received February 20th, 1894..) 



Though a great deal has been written on the anatomy 

 of the Stem of Calamites, the references in the literature to 

 its primary structure, that is, the structure previous to the 

 commencement of secondary thickening, are extremely few. 

 Binney, who was struck with the fact that the size of the 

 specimens met with varies within wide limits, refers 1 to 

 small stems which were not more than 3/50 of an inch in 

 diameter, but even in these secondary thickening had 

 begun, for his description shows that a zone of secondary 

 xylem, at least two elements in thickness, had already been 

 developed. Solms-Laubach remarks that " almost all the 

 petrified specimens which have been examined show the 

 presence of secondary wood," and gives no description of 

 the stage where such wood is absent ; while Schenk 3 

 candidly confesses that in all the sections seen by him the 

 formation of secondary wood had already begun. It is only 

 in Williamson's fine series of Memoirs that any account of 

 the early condition of a Calamitean stem is to be found, and 

 this is given in the ninth Memoir, which was published in 

 1878. 



In that Memoir* Williamson describes several stems 

 which were still in an early stage of development, but in 



1 Observations on The Structure of Fossil Plants, Part I., p. 16. Palaeon- 

 tographical Society, 1868. 



2 Fossil Botany, p. 295. 

 3 Die fossilen PJlanzenreste, p. 107. 

 4 Philosophical Transactions, 1878, p. 322. 



