io8 The Ottawa Naturalist. [J"ly 



was referred to the Salisburiaccce, in which it was ranged with 

 Dicranophyllum, Rhipidopsis^ Trichopifys, Ginkgophyllnniy and 

 BaierUy the earlier relatives of the living genus Ginkgo. This 

 reference, which was accepted by Schenck, ' appears to find favour 

 with most foreign paheobotanists- who have more recently con- 

 sidered the relationship of the American genus, though Solms- 

 Laubach,^ regards it as based on too. slender evidence. 



In the absence of any precise knowledge of the florescence or 

 fruits of Whittlesey a ^ any systematic reference of the genus is based 

 almost wholly on the characters and analogies of the leaves, and 

 must therefore be regarded as hypothetical and tentative. Yet 

 the development and the nervation of the leat are such as prac- 

 tically to exclude a comparison with any Cryptogamic type, and to 

 at once suggest a gymnospermic nature. Further, the analogies 

 between the leaf structure of Whittleseya a.nd those of Ginkgo, and 

 more particularly with the more ancient forms of that type, are so 

 striking as to compel a comparison with both the living and the 

 fossil representatives of the Ginkgoales. These analogies are 

 illustrated by the almost identical characters of the nervation and 

 distal border of the leaf in Whittleseya microphvlla and in the 

 recent Ginkgo. Among some of the additional Appalachian Potts- 

 ville material, which will probably receive special attention in - a 

 later paper, are several fragments which appear to indicate a 

 probably spiral arrangement of the leaves, the latter forming, in 

 W. microphylla, very loose tufts at the ends of the twigs. 



There are also two conditions which favour a direct relation- 

 ship of the American type to the Ginkgoales : First, there is the 

 extraordinary antiquity of the genus Ginkgo which is clearly iden- 

 tified in the older Mesozoic,while its antecedents or closer relatives, 

 Baiera and Ginkgophylluni, are present in the Permo-Carbon- 

 iferous, in which are also found a number of the immediately allied 

 types. In this connection it will be of interest for the reader to 

 compare the Whittleseycs with the group illustrations of Ginkgo 



^ Die fosb. Pflanzenreste, i8S8, p. i66. 



"^ See Zeiller, Elem. de palt^obot., 1900, p. 251. Also see Seward and 

 Gowan, in Annals Bot., vol. XIV, 1900, p. 135. 

 * Fossil Botany, 1891, p. 66. 



