INTRODUCTION. 



A paleontologist, located for more than half a century near the centre of an 

 area throughout which the Carboniferous rocks predominate, I have necessarily 

 been brought into constant contact with various forms of Stigmaria ficoides. Not- 

 withstanding these advantages I long participated in the ignorance which prevailed 

 so widely respecting them ; but the discovery, especially in the districts round 

 Oldham and Halifax, of those remarkable coal-seams overlying the Millstone Grit, 

 from which such rich harvests have been reaped during the last twenty years, has 

 materially altered the position of students of Stigmaria. During that period, I 

 have collected every fragment of the plant calculated to throw light upon its 

 structure and affinities, and I think T may express my belief that my cabinets now 

 contain the largest collection of such illustrative specimens in existence. 



Under the impression that I now possess the materials for drawing up a history 

 of Stigmaria ficoides which would contain but few blank places, the time seems 

 to have arrived for placing such a history in the hands of geologists, though there 

 are, even yet, some features of the organism respecting which we require more know- 

 ledge. The publication of a fair report of what we do know will probably facilitate 

 the acquisition of what is yet wanting. I am fully satisfied that Stigmaria, 

 viewed as an organ, 1 is a root ; I am equally so that it is the root of various 

 species of Sigillaria and Lepidodendra. Hence it is far from improbable that 

 specific differences may one day be found amongst the objects which we now know 

 by the name of Stigmaria ficoides; but at present we have wholly failed to dis- 

 cover any such differences. 



Though our knowledge of the structure of the aerial stems of Sigillariae and 

 Lepidodendra is steadily increasing, we yet require more than is at present within 

 our reach ; but this is already sufficient to correlate, with a fair measure of probable 

 accuracy, the relationship existing between the tissues of these aerial stems and 

 those of their Stigmarian roots. We have abundant evidence respecting the 

 external features of that relationship, but we have yet to discover the actual junc- 

 tion of the vascular, exogenous or centrifugally developed, cylinder of the root with 



1 I employ this term as it is used by Prof. De Bary, i.e. as the instrument of physiological work. 

 See ' Comparative Anatomy of the Phanerogams and Ferns,' English Translation, p. 1. 



1 



