182 D. H. Scott. 



Lancashire. The branched rhizome is traversed hy an almost cy- 

 lindrical stele, the wood of which consists of two parts: the centre 

 is occupied, as in Zygopieris . hy small tracheides scattered among 

 parenchyma, while the main part of the wood forms a broad surround- 

 ing zone of much larger elements. The point of interest is that the 

 outer zone has its elements radially arranged, constituting, to all 

 appearance, a secondary tissue, just as is the case in Botrychium 

 among recent Ferns. Otherwise the fossil bears considerable resem- 

 blance to Zijgopteris corrugata; anatomically BotrychioxijJon shows a 

 relation to Zygoptcris. like that of Boirychium to Ophioglossum, and it 

 is on this ground that the name of the fossil genus has been selected. 

 I hope to describe this curious stem, which presents some difficulties 

 of interpretation, on another occasion; in the mean time it may be 

 worth recording here as the only case as yet noticed among plants 

 of the Botryopteridian t3'pe, in which there is evidence of secondary 

 growth. 



In the present state of our knowledge, it is clearly impossible to 

 give a strict definition of the family Botryopterideae, or to fix its 

 limits with certainty. A wider knowledge of the reproductive organs 

 is especially needed before this can be undertaken. Renault, who 

 first established the familj', traced a relationship to the Hymeno- 

 phyllaceae, Osmundaceae and Ophioglossaceae ; he was subsequently 

 led by the supposed evidence of heterospory to assume an affinity 

 with Salviniaceae, a view which no longer ai)pears tenable. In 1900 ^) 

 I pointed out, in agreement with Eenault, that on the characters of 

 the sporophylls and sporangia the nearest comparison appeared to lie 

 with the Osmundaceae and Ophioglossaceae, while the anatomy and 

 mode of branching of Zygopieris showed the closest analogies with 

 Hymenophyllaceae. I regarded the group as a synthetic one, not 

 improbably representing the stock from which some at least of the 

 families of recent Ferns were derived fp. 299). A similar view has 

 more recently been expressed by Mr. K i d s t o n who says : "In regard 

 to the true Ferns it seems probable that they may have been derived 

 from the Botryopterideae." -) Mr. A r b e r regards the Botryopterideae 

 as but one imi)ortant family of the ancient race of Ferns to which 

 he gives the general name of Primofilices, and considers it more than 

 probable that this race gave rise to the Leptosporangiatae (Arber, 

 1906, p. 221). In another passage he saj^s (1. c. p. 227). "It may be that 

 in Palaeozoic times the Fern line of descent had not yet become clearlj^ 

 differentiated into Eusporangiate and Leptosporangiate," and adds, 

 "Possibly the origin of the Eusporangiatae is to be also sought for in 



^) Studies iu Fossil Botany, p. 297. 



^) Kids ton, Microsporangia of Pteridosperms. abstract, p. 162, 1906. 



') On the Past History oi the Ferns, Ann. of Bot., Vol. XX, July, 1906. 



