Tree (Ginkgo hi lob a , Li). 119 
The leaves of Ginkgo are of considerable importance as 
evidence of the occurrence of the genus in former periods of 
the earth’s history; their characteristic shape and venation 
render them more trustworthy than most leaves as aids in the 
identification of fossils. Reference is made by the earliest 
writers on Ginkgo to the Fern-like form of the leaves, which 
are aptly compared with the leaves of some species of Adi- 
an turn. Among existing Gymnosperms there are no species 
of which the leaves bear more than a distant resemblance to 
those of the Maidenhair tree. Among Angiosperms, an 
Australian plant, Hakea BaxterT , R. Br., possesses a leaf 
similar in form to that of Ginkgo , but easily distinguished by 
the venation. It is to the fronds of Ferns that the leaves of 
Ginkgo approximate most closely; the reniform fronds of 
such species as Adiantum reniforme , L. 1 2 , A Parishii , Hook. 3 , 
Trichomanes reniforme , Forst., Linds ay a reniformis , Dry. 4 , 
Pterozonium ( Gymnogramme) reniforme , Mart. 4 , present a 
fairly close agreement with the leaves of the Maidenhair tree, 
but the characteristic leaf of the latter, with its more or less 
deep median incision 5 , and less distinctly cordate base, 
may usually be readily distinguished from the fronds of Ferns. 
In PI. IX, Fig. 30, half of a frond of Scolopendrium nigripes , 
Hook. 6 , is represented ; this illustrates a type of leaf very 
different from that of the British species and very similar to 
Ginkgo , from which it differs in the anastomosing veins. 
A leaf of similar form has been figured by Clarke as Scolo¬ 
pendrium Delavayi , Franck 7 . 
The leaf of Ginkgo , as shown in Figs. 62-66 and 70, is 
characterized by the long and slender petiole and the broadly 
obcuneate lamina; the upper margin is usually somewhat 
uneven and irregular in outline, the base may be either 
1 Hooker, W. J. (’ 42 ), PI. CDXXXIX and CDXL. 
2 Ibid. (’ 46 ), PL LXXI a. 3 Beddome (’ 65 ), PI. XVI. 
4 Engler and Prantl, Nat. Pflanz., Polypodiaceae, p. 256, 1899. 
5 Cohn (’ 96 ), p. 130, quotes some lines written by Goethe on the bilobed leaf of 
Ginkgo. 
6 Hooker, W. J. (’ 57 ), PI. IX; vide also Watson (’ 98 ). 
7 Clarke (’ 90 ), p. 93, PI. XLI. 
