28 A SUMMER IN GREENLAND 
Gleichenia) living to-day in tropical and sub- 
tropical countries; there are also twigs of Conifers, 
some of which are almost identical with those of 
the Mammoth tree (Sequoia (Wellingtonia) gigan- 
tea now confined to a narrow strip of the, Cali- 
fornian coast), and massive stems of forest trees. 
None of the leaves preserved in the Greenland 
rocks have a greater fascination for the student of 
the past history of living plants than those of the 
genus Ginkgo. This genus is now represented by a 
single species, the Maidenhair tree (Ginkgo biloba), 
which is sometimes said to occur in a wild state in 
China, though it is probable that even in China 
and Japan, where it grows abundantly, it is only 
as a cultivated tree associated in the oriental mind 
with some religious symbolism. Ginkgo is often 
planted in gardens and parks in Europe and 
America and is distinguished from all other trees 
by its broad and often lobed, wedge-shaped leaves. 
Fossil leaves, some indistinguishable from those 
of the sole survivor of this ancient genus, have 
been found in the Cretaceous sediments on Uper- 
nivik Island (Map B), in sedimentary rocks asso- 
ciated with basaltic lavas at Sabine Island (lat. 
75° N.) on the east coast of Greenland, at several 
localities within the Arctic Circle, also in many 
other regions of both the Old and the New World. 
These records afford an exceptionally striking 
illustration of the possibilities offered by a study 
of the herbaria of the rocks of connecting the 
present with the past, of following the wanderings 
over the world and of tracing the rise and fall in 
