MEDULLOSEAE 445 



In both the species of Medullosa just mentioned, 

 the leaf- traces are given off from the outermost 

 steles. In M. Solmsii, however, where there is a 

 double zone of peripheral steles, it appears that 

 the bundles arise from the inner ring. In no case 

 were the more central cylindrical steles directly 

 connected with the leaf- traces, though there was 

 indirect communication, by means of fusions with the 

 peripheral system. 



Our knowledge of the foliage of the Continental 

 Medullosae is a matter of inference. M. Leuckarti, as 

 already mentioned, bore leaf- stalks with the structure 

 of " Myeloxylon Landriotii" and we know, from M. 

 Renault's 1-esearches, that petioles with that structure 

 belonged to Alethopteris. There is therefore a strong 

 presumption that the foliage of Medullosa Leuckarti, 

 like that of M. anglica, was of the Alethopteris type. 

 M. Leuckarti seems to have had a short stem, and may 

 have been of almost herbaceous habit. From the 

 structure of the leaf-traces in M. stellata, which includes 

 the largest specimens of the genus, there is little doubt 

 that its petioles were also of the " Myeloxylon " kind, 

 but we have no more direct evidence as to the nature 

 of the leaf. 



"Myeloxylon" petioles, of the type named by M. 

 Renault M. radiatum, characterised by the radially 

 elongated hypodermal bands of sclerenchyma, were 

 shown by him to belong to the genus Neuropteris. 

 There is therefore strong evidence that the latter genus, 

 as well as Alethopteris, consisted, wholly or in part, of 

 the foliage of species of Medullosa. Fern-like leaves 

 of certain other genera, such as Odontopteris, Callipteris, 



