XL] GESrKGOITES 11 



the confirmatory evidence of flowers and seeds. From Wealden 

 and Jurassic, rocks numerous leaves have been described that in 

 some cases are practically identical with those of the hving species, 

 but for the most part they are characterised by certain features 

 denoting at least a specific difference. For these and for other 

 Grinkgo-like leaves it would seem desirable to follow the usual 

 custom and adopt a designation that does not necessarily imply 

 even generic identity. A few examples of seeds and male fiowers 

 are known from Jurassic strata bearing a close resemblance to 

 those of Ginkgo hiloba, but such specimens are not common and 

 some of the few that have been found, though probably belonging 

 to the Ginkgoales, may not be correctly included in Ginkgo. 

 I therefore propose to employ the name GinJcgoites for leaves that 

 it is beheved belong either to plants generically identical with 

 Ginkgo or to very closely alUed types. 



It is impossible in some cases to draw a sharp line between 

 the genera Ginkgo and Baiera: typical examples of the latter 

 genus are easily recognised by their narrow, relatively longer, 

 and more numerous segments^ but it is obvious that characters 

 based on the degree of division of a lamina and on the breadth 

 of the segments are at best unsatisfactory, and the inclusion of 

 certain specimens in one or other genus is purely arbitrary. 



A difficulty is presented by several types of Palaeozoic leaves 

 assigned by many authors to the Ginkgoales and referred to 

 Ginkgophyllum, Psygmophyllum, and other genera which, while 

 bearing a general resemblance to the leaves of Ginkgo, cannot be 

 regarded as evidence of the occurrence of the class that is now 

 represented by Ginkgo biloba. It has been suggested that Psygmo- 

 phyllum, Ginkgophyllum, Rhipidopsis, and certain other genera 

 should be included in a distinct group, the Palaeophyllales^, a 

 - group of which the affinities are unknown. Though the adoption 

 of a distinctive group-name has the advantage of indicating the 

 absence of any trustworthy evidence of relationship to the Ginkgo- 

 ales, it is open to question whether anything substantial is gained 

 by the use of a term suggestive of relationship between different 

 leaves that in themselves afford no clue as to the position of the 

 parent-plants. 



1 Arber, E. A. N. (12) p. 405. 



