142 Seward and Gowan .— The Maidenhair 
Among other Tertiary species there are Ginkgo reniformis , 
described by Heer 1 from Siberia ; G. borealis from the west 
coast of Greenland, and G. Laramiensis , Ward (probably 
identified with G. adiantoides ), from the Laramie beds of North 
America 2 . 
Flozvers and seeds. The existence of Palaeozoic seeds very 
closely allied to those of Ginkgo has already been noticed. 
There is a strong probability that some at least of the Ginkgo- 
like leaves of Palaeozoic age were borne by plants possessing 
no distant affinity with the recent species, but how near the 
relationship between the past and present types was it is 
impossible to decide. Our knowledge of many of the 
Gymnospermous seeds from Permian and Upper Carboniferous 
horizons is fairly complete so far as concerns their internal 
structure, but we have little knowledge as to the plants 
which bore the seeds. It would seem probable that there 
existed in the Permo-Carboniferous forests extinct types, 
such as Cordaites and other genera, which cannot be fitted 
into any of our existing families, but possessed certain 
characters, in either their vegetative or reproductive organs, 
which have persisted as characteristic features of the Maiden¬ 
hair tree of to-day. 
The recognition of certain characteristics of the Ginkgo- 
aceae in Palaeozoic types does not by any means demonstrate 
the existence or even the probable existence of the family 
in Permian or Carboniferous times, but it is more in 
accordance with experience to expect that extinct genera 
of so remote an antiquity should exhibit points of affinity 
with more than one existing family. The plants which 
possessed characters nearest akin to those of Ginkgo were 
probably members of the Cordaitales, an extinct stock with 
which the Ginkgoaceae are closely connected. 
The best examples of flowers of Mesozoic age which may 
reasonably be referred to plants bearing leaves of either the 
Ginkgo or Baiera type are those described by Heer and 
Schenk. Associated with the numerous Ginkgo leaves in 
1 Heer (’68-83). 2 Ward (’86), PI. XXXI. 
