﻿12 SCOTT, Early History of Seed-bearing Plants. 



1832 and named by him Medullosa* The relation of the 

 various organs is very well shown in the British species, 

 Medullosa anglica, discovered a few years ago (Scott, '99), 

 in which the leaf-bases, with typical Myeloxylon structure, 

 are still attached to the stem, with which the adventitious 

 roots are also in connection. The foliage of this species 

 was that of an Alethopteris, very probably identical with 

 the well-known A. lonchitica. The stem, like that of the 

 more highly organised ferns, contains several vascular 

 cylinders (usually three in the British species) but each of 

 these cylinders surrounded itself with a zone of secondary 

 wood and bast, produced by the activity of a special 

 cambium. Thus the structure of an old stem comes to 

 simulate that of an anomalous Cycad, as is more especially 

 apparent in some of the highly complex continental 

 species. The structure of the petiole, with its numerous 

 vascular bundles, has in almost every detail a Cycadean 

 character, though in form and venation the fronds (as in 

 the recent Cycad Stangerid) are like those of a fern. The 

 root-structure also finds its nearest analogy in that of 

 Cycadaceae. Thus we recognize here also, a combination 

 of Cycadean with Filicinean characters, the primary 

 organization of the stem and the external characters of 

 the frond pointing to ferns, while in all other respects the 

 structure of Cycads is approached. On these grounds the 

 Medulloseae, like the Lyginodendrese have been placed 

 since 1897 in the class Cycadofilices. The Medulloseae, 

 founded on anatomical characters, and the Neuropterideae, 

 distinguished by the external features of the frond, are, to 

 a great extent at least, co-incident, so that in this case also 

 we have an important group of fern-like fronds, shown by 

 their structure to have belonged to plants very different 

 from true ferns. 



* This discovery was originally made by Weber about the year 18S0, but 

 the evidence was not fully published till 1896. 



