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III. On the Organisation of the Fossil Plants of the Coal-Measures. —Part XV. 
By William Chawfoed Williamson, LL.D., F.R.S., Professor of Bota7iy in the 
Owens College, Manchester. 
Received June 13,—Read June 21, 1888. 
[Plates 1-4.] 
Some years ago M. Renault described* some specimens of petioles of Ferns, which 
he identified with Gouda’s genus Zygopteris, identical, in part, with Cotta’s genus 
Tubicaulis. In my memoir. Part VI.,t I described, from the lower Carboniferous 
rocks of Lancashire, two of M. Renault’s species, viz., Zygopteris Lacattii and 
Z. hibractensis ; but, from an unwillingness to multiply genera based only upon the 
ill understood fragments of imperfectly known plants, I proposed {loc. cit., p. 677) 
the provisional adoption of the neutral generic term Rachiop>teris for a considerable 
number of these objects, which appeared to be either rhizomes or petioles of 
Ferns. Subsequent researches have, I think, shown the wisdom of doing so ; at all 
events, further discoveries, which I now propose to put on record, unmistakably 
confirm my opinion. 
In the same memoir (Zoc. cit., p. 173) M. Renault described a rhizome, with 
petioles, the latter of which closely resembled those of Coeda’s genus Ariachorop)teris, 
and to which the French palseontologist gave the name of Anachoropteris Decaisnii. 
But the structure of the rachis of this plant, especially of the transverse section of 
its vascular bundle, was wholly different from that of any plant previously observed. 
Having obtained a stem identical with this Anachoi'opteris, but without any 
petioles connected with it, I figured my specimen in my memoir. Part VI., Plate 58, 
fig. 51, where I described it as closely resembling M. Renault’s Anachoropteris 
Decais7iii. 
It must be remembered that Coeda’s two genera, Anachoropteris and Zygopteris, 
were solely based by him upon distinctions between the transverse sections of two 
petioles. That author knew nothing of the nature of the rhizome of either of these 
petioles. M. Renault, however, obtained a rhizome associated with a petiole closely 
identical with that of Coeda’s Ziygopteris, which he described'" under the name 
of Zygopteris Brongniai'tii. He thus possessed Coeda’s two forms of petiole asso- 
* ‘ Annales des Sciences Natnrelles,’ 5*^™® Serie, Bot., vol. 12, 1869, p. 161. 
t ‘ Phil. Trans.,’ vol. 164, 1874. 
X 2 
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