ADDITIONS TO THE FLORA OF THE WILCOX GROUP. 



11 



lections are available, whether it be from the 

 Denver formation, the Raton formation, or 

 the Wilcox group, all or nearly all the forms 

 are found associated in the same stratum. 

 Fifteen to twenty species of a single genus do 

 not grow together in nature. 



If these forms are considered to represent a 

 single variable species, then the earliest name 

 available is mississippiensis, given by Les- 

 quereux to what he regarded as a species of 

 ( 'innamomum. It is true that this form was 

 rather small in size, but the type is no longer 

 in existence and the later material identified 

 as this species is larger. For example, the form 

 so named in the Raton flora is identical with 

 the associated forms referred to Ficus pseudo- 

 popvlus. The type of this last-mentioned 

 species was also based on small forms, which 

 do not, however, differ in any essential respect 

 from the larger leaves later determined, and 

 the maximum of size and elongation is furnished 

 by the forms from the Wilcox figured in the 

 present contribution. I have not included 

 Ficus denveriana in the foregoing synonymy, 

 as it prevailingly lacks the three primaries and 

 is pinnate veined. However, certain speci- 

 mens so called appear to belong here, as, for 

 example, the specimen shown in figure 5 on 

 Plate XXXIII of Lesquereux's "Tertiary 

 flora." 



mississippii nsis would be the transformation 

 of the basal secondaries into lateral primaries. 

 As triveined forms of Ficus are not uncom- 

 mon in the Upper Cretaceous the ancestral 

 stock of Ficus mississippiensis may go back to 

 some such form as Ficus ovatifolia Berry, of 

 the Coastal Plain Cretaceous, or Ficus prae- 

 trinervis Knowlton, of the Yermejo formation, 

 and Ficus denveriana may be unrelated or else 

 represent the transformation of lateral pri- 

 maries into basal secondaries. 



Discussion may be eliminated by presenting 

 the supposed interrelationship diagrammati- 

 cally in terms of the specific names of the 

 above synonymy, as follows: 



planicostata 



planicostata maxima 



occidentalis 



neoplanicostata 



pseudopopuhis 



The maxima of these two lines of variation 

 are shown in the accompanying figures, and 

 no detailed description of them is regarded as 

 necessary. A statement regarding the recorded 

 geographic and geologic range of the species 

 may not, however, be out of place. This may 

 be presented in tabular form, as follows: 



Ficus planicostata Lesquereux represents 

 variants with a foreshortened apex, although 

 the smaller leaves of this so-called species as 

 figured by Lesquereux are indistinguishable 

 from the small leaves of Ficus neoplanicostata 

 figured by Knowlton. 



If the central stock of this variable species 

 is considered to have been an elliptical-ovate 

 penniveined form similar to the typical Ficus 

 denveriana Cockerell or to the young leaves 

 referred to Ficus neoplanicostata, then the 

 assumption of the specific character of Ficus 



It may be noted that only one of these 

 species, namely, F. planicostata, is recorded 

 from a pre-Tertiary horizon, and that all are 

 found associated in both the Wilcox and Raton 

 floras, Ficus richardsoni Knowlton of the Raton 

 not being an exception to this statement, for it 

 is obviously identical with Ficus pst udopopulus. 

 Occurrences in the Wilcox range throughout 

 the group and are as follows : 



Ackerman formation: Raglans Branch, Lafayette Coun- 

 ty, Miss.; Colemans Mill, Choctaw County, Miss.; Hurleys, 

 Benton County, Miss. 



