264 
de Fraine. — On Medullosa centrofilis. 
The hypodermal zone is of Renault’s Myeloxylon Landriotii type. 
2. Affinities (Section vii, pp. 261-262). There is close agreement with 
Medullosa anglica and M.pusilla , not only in general organization but in the 
details of the leaf-base structure and of the vascular system of the stem. 
The small size, the differing phyllotaxy, the absence of secondary tissues 
from the leaf-trace when emerging from the stele, and, more particularly, 
the presence of the central star-ring, are the main reasons for assigning 
specific rank to the specimen. 
The fossil is regarded as belonging to the same ‘ form-cycle ’ as 
Medullosa anglica and M. pusilla. The central star-ring foreshadows the 
type of structure characteristic of the Permian members of the genus, and 
more particularly such a type as M. Leuckarti. 
Literature. 
Bancroft, N. : III. Rhexoxyhn africanum , anew Medullosean Stem. Trans. Linn. Soc. Lond., 
Ser. 2, Bot., vol. viii, Pt. II, 1913. 
de Fraine, E. : On the Structure and Affinities of Sutclipfia , in the Light of a newly discovered 
Specimen. Ann. of Bot., vol. xxvi, No. civ, Oct. 1912. 
Goppert, H. R., and Stenzel, G. : Die Medulloseae. Eine neue Gruppe der fossilen Cycadeen. 
Kassel, 1881. 
Kisch, M. H. : The Physiological Anatomy of the Periderm of Fossil Lycopodiales. Ann. Bot., 
vol. xxvii, No. cvi, April, 1913. 
Scott, D. H. : Studies in Fossil Botany, 2nd ed., Pt. II, 1909. 
: On the Structure and Affinities of Fossil Plants from the Palaeozoic Rocks. III. 
On Medullosa anglica , a new Representative of the Cycadofilices. Phil. Trans. Roy. Soc., 
Ser. B, vol. cxci, 1899. 
: On Medullosa pusilla. Proc. Roy. Soc., B., vol. lxxxvii, 1914. 
Seward, A. C. : On the genus Myeloxylon (Brong.). Ann. of Bot., vol. vii, p. 1, March, 1893. 
Weber, O., and Sterzel, J. T. : Beitrage zur Kenntniss der Medulloseae. Ber. der naturw. Ges. 
zu Chemnitz, vol. xvii, 1896. 
Worsdell, W. C. : The Structure and Origin of the Cycadaceae. Ann. of Bot., vol. xx, April, 1906. 
explanation of PLATE XV. 
Illustrating Dr. E. de Frame's paper on Medullosa centrofilis. 
The photographs were taken by Mr. F. Pittock, of the Zoological Department, 
University College, London. 
a, /3, 7, 7 1 and 7 2 = steles : 8 = star-ring ; lb. 1 , lb. 2 , lb. 2 , and lb? = leaf-bases ; sc. 1 , 
sc? = sclerenchyma fibres; sc.b. = fibrous zone; hy. — hypoderma ; pd. = periderm; It. = leaf- 
trace ; st. = stele ; m.c. = secretory canal ; s. = sheath ; c.b. = cambium. 
Fig. 1. Transverse section of stem (Section A), showing three of the leaf-bases : part of leaf- 
base 1 (on the right) omitted, x 2-5. 
Fig. 2. Transverse section of the stem (Section 9). x 2*5. 
Fig. 3- Part of Section B, showing part of leaf-base lb? cut off by the sclerenchyma zone 
sc?, x 17*5. 
Fig. 4. Leaf-trace 1 which has just emerged from the stele, st. ; a second leaf-trace, It?, has 
divided. From section 8. x 17*5 
