257 



later auttors as Ginkgo Suttoni ; this fossil form may, however, be 

 closely matched with the more deeply lobed leaves frequently met 

 with on the recent species. While including both forms of leaf 

 under one specific name, it may be convenient to distinguish the 

 more deeply lobed type by adding the term Huttoni as marking 

 a ' form ' or variety of the species G. digitata. 



Brong-niart ^ defined the species Cyelopteris digitata as follows : — 

 " Cyelopteris foliis petiolatis, semiorbiculatis, flabellitormibus, ad 

 margLnem lobatis, lobis contiguis cuneiformibus truncatis vel 

 ad apicem sinuosis, nervis tenuissimis striseformibus sequaUbus." 

 Brongniart compares the leaves with those of Trichomanes reniforme. 



The drawing given in Phillips' work (pi. vii. fig. 18) is far 

 from accurate ; it is impossible to detect in the specimen anything 

 corresponding to the three small lobes shown at the base of the 

 leaf. The type-specimen represents a typical example of a Ginkgo 

 leaf with a divided lamina ; it is twice the size of the drawing, 

 as indicated in PhiUips' figure. Goppert, like Brongniart and 

 other authors, placed the Ginkgo leaves in a genus denoting 

 a fern affinity. Braun included Cyelopteris digitata, Brongn., in 

 his new genus Baiera, which he compared with Marsilia, on the 

 strength of a supposed resemblance of what he took for reproductive 

 structures to the sporocarps of that genus. 



In the fourth volume of his Flora fossilis Arctica, Heer 

 discussed the affinity of Cyelopteris digitata, Brongn., and allied 

 Jurassic species, which he described from Spitzbergen ; he pointed 

 to certain characteristics in the venation of the lamina and to the 

 grooved surface of the petiole of the fossil leaves as reasons for 

 regarding the leaves as generically identical with those of Ginkgo 

 hilola? Heer also described specimens of male flowers and seeds 

 associated with several of the fossil leaves, and these he naturally 

 regarded, from their very close resemblance to the flowers of the 

 recent species, as belonging to the plant which bore the leaves with 

 which they were found in close association. 



The species Cyelopteris incisa, described by Eichwald from 

 Russia, is of the same form as some of the English Ginkgo leaves 

 from the Yorkshire coast ; it agrees closely with the example 



> Brongniart {28*), p. 219. 

 '. Heer (77'), p. 41. 



