I 



92 



THE GEOLOGICAL HISTORY OF PLANTS. 



inches in diameter, rugose longitudinally. Leaf-scars broad, rounded 

 above, and radiatingly rugose, with an irregular scar below, arranged 

 spirally in about five ranks; vascular bundles not distinctly pre- 

 served. Petioles slender, much expanded at the base, dividing at 

 first in p. piimate manner, and afterwards dichotomously. Ultimate 

 pinnae with remains of numerous, apparently narrow pinnules. 



This stem is probably the upper part of one or oth r of the 

 species of Psaronius found in the sanie bed (P. Erianus, Dawson, 

 and P. fextilis, Dawson).* It appears to have been an erect stem 

 embedded in situ in sandstone, and preserved as a cast. The stem 

 is small, being only two inches, or a little more, in diameter. It 

 is coarsely wrinkled longitudinally, and covered with large leaf- 

 scars, each an inch in diameter, of a horseshoe-shape. The peti- 

 oles, five of which remain, separate from these scars with a distinct 

 articulation, except at one point near the base, where probably a 

 bundle or bundles of vessels passed into the petiole. They retain 

 their form at the attachment to the stem, but a little distance 

 from it they are flattened. They are inflated at the base, and some- 

 what rapidly diminish in size. The leaf-scars vary in form, and are 

 not very distinct, but they appear to present a semicircular row of 

 pits above, largest in the middle. From these there proceed down- 

 ward a series of irregular furrows, converging to a second and more 

 obscure semicircle of pits, within or below which is the irregular scar 

 or break above referred to. The attitude and form of the petioles 

 will be seen from Fig. 24, supra. 



The petioles are broken off within a few inches of the stem ; 

 but other fragments found in the same beds appear to show their 

 continuation, and some remains of their foliage. One specimen 

 shows a series of processes at the sides, which seem to be the re- 

 mains of small pinna), or possibly of spines on the margin of the 

 petiole. Other fragments show the division of the frond, at first in 

 u pinnate manner, and subsequently by bifurcation ; and some frag- 

 ments show remains of pinnules, possibly of fertile pinnules. These 

 are very indistinct, but would seem to show that the plant ap- 

 proached, in the form of its fronds and the arrangement of its 

 fructification, to the Cyclopterids of the subgenus Aneimites, one of 

 which (Atieimites Acadica), from the Lower Carboniferous of Nova 

 Scotia, I have elsewhere described as probably a tree-fern.f The 



* Memoir on Devonian Flora, " Proceedings of the Royal Society," 

 May, 1870. 



t "Quarterly Journal of the Geological Society," 1860. . - 



