Botany— 1938 Meeting 109 



conservative by modern taxonomists so the last possibility might conceiv- 

 ably be of common occurrence in fossil plants. As a consequence of this 

 general situation the identification of the genus Medullosa is based entirely 

 on characters of the stem. Notwithstanding this handicap the leaves, 

 petioles, seeds, male fructifications and roots which go with these stems are 

 sufficiently known, either from isolated cases where the organs are found 

 in actual connection or from their constant association in the same deposits 

 or on the basis of histologic similarities, that their general relationship is 

 apparent. Thus it is known that several Medullosa stems bore foliage which 

 is classified separately as Alethopteris. Structurally preserved petioles de- 

 tached from their stems are designated as Myeloxylon. The characters 

 used in diagnosing species of either of these genera do not necessarily 

 correlate in the course of evolution with species variations exemplified by 

 the stems. 



Recently fructifications which are related in the Medullosaceae have 

 been discovered. Certain of the Medullosan seeds have been named Ro- 

 todontiospermum and male fructifications are classified under Dolerotheca 

 (in part). It is necessary to use these different names to apply to the 

 various isolated plant organs because their specific inter-correlation cannot 

 be proved with sufficient accuracy. Herein lies the chief difference between 

 the taxonomy of fossil and modern plants. It must be recognized never- 

 theless that these fossils classified under different names have a close 

 natural relationship to the stems previously discussed. In various instances 

 the relationship of assembled organs, as in the case of these mentioned, may 

 be indicated by classifying them together in a more generalized category 

 such as a family. The reconstructions of complete plants of past ages also 

 are based on generalizations of tlrs sort and they have proved a most 

 effective means of summarizing our detailed knowledge of the fossil floras. 



The foregoing discussion may serve to indicate briefly the problems 

 involved in the paleobotanic study of Medullosaceae. The new stem from 

 Nashville lends emphasis to characters which had previously received little 

 attention. Of course a great deal of study will be necessary before the bo- 

 tanical peculiarities and the relationship of this interesting group of plants 

 become fully known. It is definitely encouraging that additional specimens 

 are being discovered in Illinois coal balls because the European specimens 

 known previously left many pertinent questions unanswered. 



References 



1. Scott, D. H., On Medullosa pusilla : Proc. Roy. Soc. London, B, vol. 87, 

 pp. 222-3, 1913. 



2. Scott, D. H., On Sutcliffia insignis, a new type of Medulloseae from the 

 lower coal-measures : Trans. Linn. Soc, London, 2nd. ser., vol. 7, PI. 7, fig. 5, 

 1906. 



3. De Fraine, E., On the structure and affinities of Sutcliffia, in the light of 

 a newly discovered specimen: Ann. Bot., vol. 26. PI. XCI, fig. 1. 1912. 



4. Schopf, J. M., Medullosa distelica, a new species of the' Anglica group of 

 Medullosa: Am. Jour. Bot, Vol. 26 (4); 196-207, April, 1939. 



