XL] PHYSEMATOPITYS 9 



an exception to the general truth of Essner's conclusions and that 

 the large dimensions and rounded form of the ray-cells are features 

 of diagnostic value, though in the Tertiary specimens compared 

 by him with the wood of Ginkgo the ray-cells do not appear to 

 differ appreciably in size or form from those of true Conifers. 

 Given well-preserved material, it is not improbable that in favour- 

 able cases the characters of fossil wood might furnish adequate 

 grounds for referring it to Ginkgo : the numerous obhquely eUip- 

 tical pits in each ' field,' the swollen medullary-ray cells, and the 

 frequent crossing of the pores of the tracheal pits are the features 

 mentioned by Gothan^ who considers that the wood of Ginkgo — 

 though difficult to define precisely in an analytical key — may be 

 distinguished from that of Conifers. 



Among the specimens of wood assigned to Ginkgo there are 

 none, so far as I am aware, that can safely be accepted as entirely 

 above suspicion. In 1850 Goeppert^ proposed the generic name 

 Pkysematopitys^ for some Tertiary wood that he beheved to possess 

 the anatomical characters of Ginkgo biloba. Kraus* subsequently 

 recognised resin-cells in the wood of Goeppert's type-species, 

 Physematopitys salisburioides, and identified the specimens as the 

 root- wood of a Cupressinoxylon : he did not, therefore, include 

 Physematopitys in the hst of woods contributed by him to 

 Schimper's Traite de Paleontologie, but mentioned it as a synonym 

 of Cupressinoxylon. Beust^ and Barber^ among other authors 

 adopt the same course. It has more recently been stated by 

 KrauseF that Goeppert's genus Physematopitys has the characters 

 of Protopiceoxylon. Goeppert' afterwards described a second 

 species, Physematopitys siwcinea, founded on a tangential section 

 of a piece of OHgocene wood from the Baltic amber, but the 

 data are clearly insufficient to justify its identification as Ginkgo : 

 Conwentz* includes the specimen in Pinus succinifera. 



Schroeter^" described some wood from beds on the Mackenzie 

 river in North Canada, referred to the Miocene period, as Ginkgo sp. 



1 Gothan (05) p. 103. * - Goeppert (50) p. 242, PI. xLix. figs. 1—5. 



^ ipijffTina, that which is blown out. 



« Kraus in Schimper (72) A. p. 370; Kraus (83) ; Schenl< in Zittel (90) A. p. 871. 



* Beust (85). " Barber (98). ' Krausel (13). 



» Goeppert and Menge (83) A. p. 32, PI. x. fig. 74. 



« Conwentz (90) A. p. 26. " Schroeter (80) p. 32, PI. iii. fig. 27—29. 



