﻿4 SCOTT, Early History of Seed-bearing Plants. 



Lyginodendron indicated a clear affinity with Gymnosperms 

 of the Cycadean group, rather than with ferns. Yet even 

 in the stem fern-like features are not wanting. In favourable 

 cases young stems have been met with, before the cambial 

 activity had set in, and consequently at a stage when the 

 primary structure existed unaltered. Such young stems 

 present a striking similarity to those of the Osmundaceae 

 among recent ferns. 



Williamson after a time succeeded in tracing the 

 connection between the stem and its leaves, proving that 

 the petioles of Lyginodendron^ as he had suspected from 

 the first, were identical with the fossil previously named 

 Rachiopteris aspera, (Williamson, '90). The petioles,, 

 again, were found to branch freely, forming a highly 

 compound rachis which bore characteristic, lobed leaflets. 

 The form of the whole leaf was sufficiently clear in the 

 petrified specimens to admit of its certain identification 

 with the frond Sphenopteris HoningJiausi Brong., long 

 familiar in the form of impressions. {See PI. III., Fig. 1). 

 While the external morphology of the foliar organs was 

 thus shown to have been wholly fern -like, the same proved 

 to hold good for their structure. The vascular bundles of 

 petiole and rachis are concentric, the bast surrounding the 

 wood, just as in a typical recent fern. Thus, in spite of 

 some differences in the minute histology, the foliage of 

 Lyginodendron oldhaminm turned out to be that of a fern, 

 in structure, as well as in form. The roots, identified a 

 little later, proved, like the stem, to show on the whole a 

 Gymnospermous type of structure, though in their young 

 condition they were not unlike those of certain ferns. 



It thus became clear that one at least of the car- 

 boniferous plants with the foliage of a fern, presented 

 characters indicating an affinity with Gymnospermous 

 flowering plants, while at the same time its relationship to- 



