228 



On Medullosa pusilla. 



foliage of Alethopteris (Pecopteridese) (Lotsy, '09, p. 725.) If we adopted 

 this division, the name of our fossil would, of course, become Pecoptero- 

 medullosa pusilla. 



The facts at present known are not, however, favourable to a division of 

 the genus Medullosa on these lines. M. Leuckarti, one of the complex Permian 

 species, bore, according to the observations of Weber and Sterzel ('96, p. 48 

 [89]), leaf-bases belonging to Myeloxylon Landriotii (Ren.), and its foliage 

 was therefore presumably of the Alethopteris type. Uncertain as this 

 conclusion may be, we clearly have no grounds for assuming that a highly 

 differentiated stelar system was necessarily associated with Neuropteris foliage. 



In the present state of our knowledge, it would only be possible to 

 subdivide the genus Medullosa on purely anatomical characters, and at the 

 present moment even this seems to me to be premature. 



REFERENCES. 



Eranke, 12. F. Franke, " Beitra'ge zjir Kenntnis der Palaeozoischen Arten von Alethop- 

 teris und Cattipteridium," ' Abbildungen und Beschreibungen fossiler Pflanzen- 

 reste, von H. Potonie,' 1912, Lief. VIII-X. 



Kidston, '93. R. Kidston, " On the Various Divisions of British Carboniferous Rocks as 

 Determined by their Fossil Flora," 'Roy. Phys. Soc. Edin. Proc.,' 1893-94, 

 vol. 12. 



Lotsy, '09. J. P. Lotsy, ' Vortrage iiber Botanische Stammes-geschichte,' Jena, 1909, 

 vol. 2. 



Renault, '75. B. Renault, " Recherches sur les Vegetaux silicifies d'Autuu. II. — Etude 

 du genre Myelopteris," ' Mem. pres. par Divers Savants a l'Acad. des Sciences,' 

 1875, vol. 22, No. 10. 



Renault, '83. B. Renault, ' Cours de Botanique Eossile,' Paris, 1883, 3me Annee> 

 Fougeres. 



Scott, '99. D. H. Scott, " On the Structure and Affinities of Fossil Plants from the 

 Palaeozoic Rocks. III. — On Medullosa anglica" ' Phil. Trans.,' 1899, B, 

 vol. 170. 



Scott, '09. D. H. Scott, ' Studies in Fossil Botany,' London, 1908-9, 2nd Edition. 

 Weber and Sterzel, '96. O. Weber and J. T. Sterzel, " Beitriige zur Kenntnis der 



Medullosese," ' XIII Bericht der Naturwissenschaftlichen Gesellschaft zu 



Chemnitz,' 1893-96. 



EXPLANATION OF PLATE. 

 Figures are from microphotographs by Mr. W. Tarns. 

 Fig. 1. — General transverse section of the stem and leaf-bases, x 3. Scott Coll. 2817. 

 Fig. 2. — The other transverse section (reversed, as compared with fig. 1). One of the 

 three steles is destroyed and another displaced, so as to appear in nearly 

 longitudinal section. One leaf-base is perfect, x 3. Scott Coll. 2818. 

 Fig. 3. — The stelar system from fig. 1 ; pd., periderm ; l.t., leaf-trace. x 11^. Scott 

 Coll. 2817. 



Fig. 4. — Part of the leaf-base, showing the hypoderma and a bundle with xylem and 

 phloem, x 45. Scott Coll. 2817. 



