5 i4 STUDIES IN FOSSIL BOTANY 



a great extent, to the Calamopityeae also. These_ 

 Pteridosperms, however, as is now abundantly proved, 

 had their nearest relationships with the Ferns, and 

 the inference appears justified that Poroxylpn also, 

 though more modified, was derived from a Filicinean, 

 rather than a Lycopodinean stock. The importance 

 of this conclusion will become evident when the Cor- 

 daiteae have been considered. 



II. The Pityeae 



Before going on to the Cordaiteae we will shortly 

 consider a group of fossil plants which, so far as our 

 limited knowledge shows, appear to lead up to that 

 family, and to form part of the wider group which we 

 call Cordaitales. 



Most of the stems in question fall under the genus 

 Pitys of Witham, 1 as emended by Goppert. 2 There 

 are three species, all from the Lower Carboniferous of 

 Southern Scotland, and all described by Witham in 

 his famous pioneer work of 1833. The species are 

 chiefly distinguished by the width of the medullary 

 rays, the principal rays being as much as seven cells 

 wide in P. primaeva, five or six cells in P. antiqua, 

 and four cells in P. Withamii. Pitys Withamii is the 

 well-known Craigleith tree, of which a trunk is set up 

 in the grounds of the Natural History Department of 

 the British Museum. A stem of this species found at 

 Craigleith, near Edinburgh, in 1830, was 47 feet in 



1 The Internal Structure of Fossil Vegetables found in the Carboniferous 

 and Oolitic Deposits of Great Britain, described and illustrated, Edinburgh, 



'833, P- 7'. 



2 " Revision meiner Arbeiten liber die Stamme der fossilen Coniferen," 

 Botan, Centralblatt. Band v. and vi. 1881. 



