146 Seward and Gowan .— The Maidenhair 
regarded by him as agreeing most closely with the wood of 
Ginkgo , has been re-examined by Kraus and identified as 
the root-wood of the Cupressoxylon type 1 . The structure 
of the stem of some Palaeozoic plants 2 exhibits points of 
resemblance to Ginkgo , but evidence of this kind leads to the 
same conclusion as that afforded by the Palaeozoic leaves; it 
demonstrates the existence of morphological features in certain 
synthetic or composite plant-types which are now met with in 
the Maidenhair tree. 
CONCLUSION. 
Our examination of the floral and vegetative structures of 
the Maidenhair tree leads us to adopt the view that this 
isolated type should be placed in a separate division of the 
Gymnosperms—the Ginkgoaceae—and no longer included in 
the Coniferae. 
In many respects Ginkgo shows a marked affinity with 
the Cycads ; like the extinct Cycadofilices, Ginkgo possesses 
both Filicinean and Cycadean characters, but while exhibiting 
traces of the union of Cycads and Ferns, it represents 
in all probability a very ancient type which may have 
been merged into the Cordaitales in the Palaeozoic era. 
Among the numerous features in which Ginkgo resembles 
the Cycadaceae, the most striking are recognized in the ovules 
and seeds, in the production of spermatozoids, and in certain 
anatomical characters referred to in the above description of 
the reproductive and vegetative organs. 
The records of the rocks demonstrate both the antiquity 
and wide geographical range of Ginkgo and allied forms 
during the Mesozoic and Tertiary periods; species of Ginkgo 
and Baiera have been discovered in almost all parts of the 
world. The majority of the older representatives of the 
Ginkgoaceae agree more closely with the genus Baiera ; in 
the Jurassic, Cretaceous, and Tertiary periods, Ginkgo itself 
1 Kraus (’ 86 ), p. 75 . 
2 e. g. Dadoxylon Pedroi , Zeill., from Permo-Carboniferous rocks of Brazil. 
Vide Zeiller (’95). 
