CYCADEAE, MEDULLOSEAE. 103 



brought out into the clearest light by a fossil form which we will now 

 consider, Medullosa Leuckarti of Goppert and Stenzel. The resemblance 

 .between Medullosa and Cycas formerly brought into prominence and much 

 insisted upon thus loses its importance, and if we nevertheless assume 

 a close relationship between this group and Cycadeae, this arises solely 

 from the great similarity in the character of the tissue in both. I would 

 add that we must enquire further whether the peripheral woody ring of 

 some Bennettiteae, in which duplication is suspected, does not also ul- 

 timately show the conditions characteristic of Medullosae. 



The form just mentioned, Medullosa Leuckarti, Gopp. and Stenz., is 

 according to the figure a somewhat shapeless fragment of stem bearing the 

 stump of a thick lateral branch l . Its cross section shows only a few rings 

 of secondary wood, some of which have the character of star-rings ; but the 

 greater part appear in the form distinguished by the authors as snake-rings. 

 These are marked by the great width of the partial pith, and also by the 

 extremely irregular shape of the flexuous ring which forms sinuses and pro- 

 jections. Wood and bast are in their normal position, and appear from the 

 figure to be well preserved ; the latter tissue contains closed plates of fibre- 

 cells. An allied form is Colpoxylon Aeduense, Ren., with respect to which 

 Goppert and Stenzel 2 , who were only acquainted with Renault's figures 3 , 

 still express some doubt. I have seen in the Paris Museum several of the 

 beautiful plates prepared from the original specimens obtained at Autun 

 and one, a present probably from Brongniart to R. Brown, in the Botanical 

 Department of the British Museum, and have satisfied myself that in this 

 species, just as in Medullosa Leuckarti. there is a variable number of broad 

 irregularly sinuous snake-rings, each of which encloses a parenchymatous 

 partial pith. Myelopitys medullosa, Corda, from the Rothliegende of the 

 North of Bohemia, may also be nearly allied to the Medullosae ; but this 

 question, owing to the small size of the fragment which Corda 4 had before 

 him, can scarcely be perfectly cleared up even by a fresh examination of the 

 specimen. 



1 See note on p. 161. a Goppert und Stenzel (11). 3 Renault (2), vol. i, t. n, f. 8. 



4 Corda (1), t. II, ff. 4-8. 



