10 GINKGOALES 



on the ground of the large size of the medullary cells : no pii 

 are described either on the tracheids or on the medullary-ray cells 

 and the unusual size of the ray-cells may well be a pathological 



j * r 



or post-mortem phenomenon. The species Physematopitys ex- 

 cellens described by Felix 1 from beds, probably Eocene in age, in 

 the Caucasus agrees with Cupressinoxylon in the presence of rows 

 of resin-parenchyma in the wood, and the depth of the rays greatly 

 exceeds that in Ginkgo biloba. Penhallow 2 described some calcined 

 wood from Upper Cretaceous beds in the Queen Charlotte Islands 

 as Ginkgo pusilla, but the reasons for assigning it to that genus are 

 not convincing. A fuller description of another specimen regarded 

 as the wood of a Ginkgo has been published by Dr Platen 3 under 

 the name Physematopitys Goepperti from material collected 

 Miocene beds in Milam County, Texas. The relatively large size 

 of the medullary-ray cells is mentioned as the chief character 01 

 which the determination was based. 



It may be said that such fossil specimens as have been referred 

 to Physematopitys or Ginkgo have very little value as records of 

 the occurrence of the genus Ginkgo : in view of the abundance of 

 leaves in Mesozoic and Tertiary strata that are hardly distinguish- 

 able from those of the surviving type it is remarkable if the 

 anatomical characters of the genus afford in themselves a trust- 

 worthy basis of identity- -that more satisfactory specimens hav< 

 not been found. 



ii. LEAVES. 

 GINKGOITES. Gen. nov. 



It has been customary to use the generic name Ginkgo both 

 for the recent species and for fossil leaves from Mesozoic and 

 Tertiary strata, and in a few cases for Palaeozoic leaves. In 

 certain instances, for example such leaves as those from the 

 Island of Mull and other Tertiary localities referred to Ginkgo 

 adiantoides (fig. 644) there can be no doubt as to generic identity 

 with the recent species and indeed, so far as concerns form and 

 venation, the Eocene leaves might well belong to Ginkgo biloba. 

 On the other hand even in the case of Ginkgo adiantoides we lack 



1 Felix (94) p. 107, PI. ix. fig. 4. 



2 PenhaUow (02) p. 43, Pis. XH., xm. 3 Platen (08) p. 143. 



