THE MAIDENHAIR TREE SEWARD 457 



very short, scale-covered axis and borne in a cluster, resembling 

 the bunch of leaves of a five-needled pine: each leaf has two or more 

 veins forked once or more. Several species of Czekanowskia are 

 known from Jurassic rocks in arctic regions, Europe, and Asia. In 

 epidermal characters the leaves conform more closely to the Ginkgo 

 pattern than to that of any other surviving Gymnosperm. 



Nothing has been written in this article on seeds or other repro- 

 ductive organs associated with Ginkgoalean leaves in widely scat- 

 tered parts of the world and in rocks of many ages: this is not be- 

 cause they are unimportant; they are of the greatest value to the 

 paleobotanist. The reason is that it is seldom possible to connect 

 together leaves and reproductive organs, owing to the fact that they 

 are preserved in the sediments of estuaries and lakes as separate 

 scraps which fell from the parent trees and were carried by rivers to 

 their resting-place. It is, however, important to note that the re- 

 mains of such reproductive organs as it has been possible to examine 

 with any degree of thoroughness, furnish valuable data supplementary 

 to evidence of affinity obtained from foliage-shoots. 



THE WORLD-WIDE WANDERING OF GINKGO AND ITS ALLIES 



A survey of the voluminous publications in which are recorded 

 discoveries of fossil plants referred on good evidence to the Ginkgo 

 alliance demonstrates the extraordinary vitality and resiliency of 

 the genera and their success as travelers over wide spaces. It would 

 extend this sketch far beyond reasonable limits were reference 

 made to all the species and the places where they have been found. 

 It is also impossible in a general summary to make comparison of the 

 distributional areas of the several genera. The black dots on the 

 map (fig. 1) indicate localities where members of the family have 

 been found in rocks ranging from Triassic to the end of the Ter- 

 tiary period. Though by no means a complete record, the map 

 serves to illustrate the light thrown by paleobotanical data on the 

 wandering of these Ginkgoalean trees never seen in life by man 

 and known only as fragments preserved in the rocks. The tenacity 

 with which a single member of this once vigorous group held on 

 to life through the ages has enabled us to read the story of its ancestry. 



CONCLUSION 



In the foregoing pages my purpose has been to present the more 

 important results of research into the history of the Ginkgo family. 

 Ginkgo biloba, the maidenhair tree, is worthy of special regard as one 

 of the most impressive examples in the plant kingdom of a link with 

 remote ages and as the sole representative in the modern world of a 

 family, which millions of years ago occupied as prominent a place in 



