288 



PITYEAE 



[CH. 



from p. antiqua in the broader and shorter form and greater 

 breadth of the medullary rays (fig. 488, A, B), also in the larger 

 tracheids and in the less crowded arrangement of the bordered 

 pits in which the circular form sometimes replaces the hexagonal 



Fig. 488. Pitys primaeva. A, transverse section of the secondary xylem; 

 B, tangential section of the secondary xylem. (From sections of the type- 

 specimen in the Edinburgh University Botanical Department.) 



type. The structure of the pith is not known, but Scott was 

 able to recognise in the partially preserved pith of a branch indica- 

 tions of primary- xylem groups and other features pointing to a 

 close resemblance to P. antiqua^. A piece of stem originally 



1 Since this chapter was written Prof. W. T. Gordon has kindly supplied the 

 following summary of his unpublished work on the genus Pitys. 



'The re-examination of Pitys primaeva and P. antiqua in the light of the 

 structure exhibited by numerous specimens of a new species recently discovered 

 in Haddingtonshire has shown that all three types are similar as regards the 

 structure of the primary wood. In each case the primary cylinder is comparable 

 with that in Archaeopitys Eastmanii [see p. 290], i.e., there are medullary as well 

 as oiroum-meduUary xylem-strands. In certain specimens of the new species, 

 Pitys Dayii, the bark and leaves are preserved and thus the details of leaf-trace 

 emission from the stem have been determined. The leaves are short and stout 

 and taper gradually to a point, quite distinct from the long, thin, spatulate Cordai- 

 tean foliage. The internal structure of the leaf renders it easily distinguishable 

 from the Cordaites type while it tends to accentuate the possible relationship of 

 Pitys with the Lyginodendreae.' 



