AFFINITIES OF LYGINODENDREAE 421 



sation of the vascular zone, both primary and secondary, 

 is what that of a Cycad would be if the mesarch 

 structure of the foliar bundles were continued down 

 from the leaves into the stem. But we now know that 

 this is precisely what occurs in certain Cycadean 

 peduncles, which are themselves portions of the stem. 



The stem-structure of Lyginodendron is, in fact, as 

 a whole rather Cycadean than Filicinean, though in 

 the young condition, before secondary growth had set 

 in, there is a clear analogy with such a Fern as 

 Osmunda. In the form and structure of the leaf 

 Lyginodendron is as Fern-like as Heterangium. In 

 both genera the abundant adventitious roots are 

 suggestive of a Fern rather than a Cycadophyte ; their 

 anatomical structure, when young, is not unlike that 

 of the roots of Marattiaceae, or some Ophioglossaceae, 

 though the secondary changes soon give them a more 

 Cycad-like character. 



The discovery of the reproductive organs, while it 

 has finally transferred the Lyginodendreae to the 

 Spermophyta, has in one important respect emphasised 

 their affinity with the Ferns. The male fructification 

 Crossotheca and the probably allied Telangium described 

 by Miss Benson bear an unmistakable resemblance to 

 the synangia, such as those of Scolecopteris and Astero- 

 theca, attributed to Marattiaceae, and also to those of 

 recent Ferns of that order. Even if all the supposed 

 Carboniferous Marattiaceae turned out to be Pterido- 

 sperms (a very improbable supposition, as shown in 

 Chapter VIII.), the Fern-like character of the micro- 

 sporangia in the latter class would only be the more 

 significant. 



