10 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1922. 



Fiats neoplanicostata Knowlton, U. S. Geol. Survey Prof. 



Paper 101, p. 303, pi. 73, fig. 4; pi. 74, figs. 2, 3; pi. 



76, fig. 4. 1918. 

 Berry, I'. S. Geol. Survey Prof. Paper 91. p. 198, 



pi. 111. fig. 1. 1916. 

 Ficus richardsoni Knowlton, U. S. Geol. Survey Prof. 



Paper 101, p. 305, pi. 76, fig. 1, 1918. 



It would seem that if the systematic work of 

 paleobotany is to be made available for the 

 general purposes of geology and botany the 

 paleobotanist must take the time to coordinate 

 and digest the results of the work on local 

 floras. There are certain general principles 

 that should guide workers in founding new 

 species, and I am thoroughly in accord with 

 the principle which holds that analysis should 

 precede synthesis, and that in describing speci- 

 mens from a new horizon or a remote geo- 

 graphic locality the presumption should pre- 

 vail that they are distinct from previously 

 described forms unless identity can be con- 

 clusively shown. Likewise there are certain 

 forms in a different category, long known and 

 hence not susceptible of this treatment — for 

 example, Podommitex lanceolatus, Asplenium 

 dicksonianum, or Sequoia reicheribachi — which 

 are obviously composite and yet which do not 

 offer any criteria for segregation other than 

 those of a stratigraphic nature. These forms 

 may well remain as they are until the progress 

 of knowledge enables the paleobotanist to 

 treat them in a scientific manner. 



In a recent study of a large and well-pre- 

 served collection from the Wilcox near Mans- 

 field, La., I have been profoundly impressed 

 with the graded variability in the leaves of 

 certain genera, particularly Ficus and Rhumnus. 

 In my report on the flora of the Wilcox group, 

 published in 1916, 18 different species of Ficus 

 were recognized, and in Knowlton's recently 

 published report on the flora of the Raton 

 formation 17 species of Ficus are recognized. 

 In both works the comparisons made appear 

 legitimate, but in neither, apparently, had the 

 broader question of interrelationship in the 

 genus received adequate consideration. To 

 revert to the representation of Ficus in the 

 Wilcox flora: Of the 18 identified forms a 

 reexamination appears to confirm the validity 

 of 13 beyond question. The remaining five 

 species, which were identified as Ficus neo- 

 planicostata, pseudopopulus, />lmiicostata maxi- 

 ma, occidentalis, and de,nveriana., represent 



ovate types with three basilar or subbasilar 

 primaries and percurrent tertiaries. As spar- 

 ingly represented in the original collections each 

 showed a certain individuality, but in the later 

 collection, where they are abundant, they show 

 every gradation in size and in the ratio of width 

 to length. 



I do not consider it possible to maintain 

 specific boundaries in this series, although the 

 extremes of size or of short-elliptical or long 

 and narrow ovate-acuminate outline are strik- 

 ingly different in aspect. 



This polymorphism, or better termed vari- 

 ability, led to the assembling of all the pub- 

 lished figures <>f the so-called species enumer- 

 ated in the foregoing synonymy. It was found 

 that these forms had been described at different 

 times by different workers and that the criteria 

 of separation were as follows: 



1. Size. 



2. Relative proportions of width to length. 



3. Shortening or lengthening of the apex. 



4. Character of base ranging from various degrees of 

 cuneate through truncate to slightly cordate. 



5. Number and spacing of the secondaries. 



6. Position of the primaries, whether basilar, subbasilar, 

 or suprabasilar. 



In all the species the general facies and 

 tertiary venation remain identical throughout. 

 It might be argued that these represent 

 generic features and that the foregoing criteria 

 of separation are legitimate specific features. 

 It may be noted, however, that most of the 

 features enumerated above are interrelated 

 and dependent upon the proportions of the 

 leaves, and it may also be noted that leaves 

 which are normally large at maturity reach 

 that normal size by growth, so that mere 

 smallness is not a specific character. However, 

 I will not quarrel with my colleagues who 

 prefer to keep the species listed in the fore- 

 going synonymy distinct — the relationships 

 sketched below hold good, whatever cate- 

 gories are used. Some will doubtless incline 

 to consider them varieties of a single botanic 

 species, but I can only think of them as varie- 

 ties in the praenuntial or formative state, with 

 the intermediate steps not yet extinct, and 

 it seems to me that all could probably have 

 been found on a single lower Eocene tree. 

 Were they ever found unassociated there 

 might be some justification for maintaining 

 their distinctness, but wherever adequate col- 



