MKDULLOSEAE 439 



agree closely with certain leaflets described by 

 M. Renault in 1883, which, as shown by their external 

 characters, belonged to an Alethopteris} The rachis 

 and petiole of M. Renault's Alethopteris showed the 

 anatomical structure of " Myeloxylon Landriotii." Thus 

 the French author's observations, taken in conjunction 

 with Weber's discovery that " Myeloxylon Landriotii " 

 was the leaf-stalk of a Medullosa, proved that the well- 

 known Alethopteris fronds were borne as foliage on 

 certain of the Medullosa stems. 



From the organisation of the petioles and leaves in 

 Medullosa anglica, there can be little doubt that the 

 English species also bore foliage of the Alethopteris 

 type, an example of which is illustrated in Fig. 162 

 from A. lonchilica, very probably the actual species 

 concerned. 



The roots of M. anglica have frequently been found 

 in connection with the stem, on which they were borne 

 in vertical series, between the leaf-bases. They have a 

 normal triarch structure, and, with increasing age, 

 formed a large amount of secondary wood and bast, 

 interrupted opposite the protoxylem-angles by large 

 medullary rays, just as in recent roots with secondary 

 growth. The detailed structure of the xylem agrees 

 with that of the corresponding tissue in the stem. Mr. 

 Arber finds that the phloem much resembles that in the 

 stem of Heterangium tiliaeoides. The groups of sieve- 

 tubes are accompanied by phloem-parenchyma, and 

 separated by dilated parenchymatous rays. The sieve- 

 tubes show the lateral sieve-plates particularly well ; 2 



1 Renault, Cours de Botanique fossile, vol. iii. p. 159, Plate xxvii. 

 2 Arber, loc. cit. Plate xx. Fig. 5. 



