﻿38O SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



tory canals and somewhat concentrically arranged vascular bundles, 

 the whole being surrounded by a thick hypodermal parenchymatous 

 zone containing numerous longitudinal sclerenchymatous strands and 

 secretory canals, and a layer of pallisade tissue. In their general 

 structure they resemble Marattiaceous petioles. 



Naturally the Medullosan stems were early regarded by most 

 paleobotanists as more or less distinctly Cycadean ; and this view 

 is supported by the structure of the petioles, in which, in some 

 species, a secondary wood accompanies the vascular strands. It 

 must, however, be remembered that collateral primary bundles ac- 

 companied by secondary wood also occur in the Ophioglossacese. 



The researches of Renault 1 have shown that the petioles (Myel- 

 oxylon) of Medullosa bear the large filicoid fronds, often tripinnate 

 and quadripinnate, of the two great frond genera Neuroptcris and 

 Alethofteris, which previously had been generally considered as 

 comprising the most common and characteristic Carboniferous ferns. 2 

 A portion of a frond of Neuroptcris, from the Upper Carboniferous 

 of Alabama, is shown in plate lv. 



As long ago as 1889 Mr. Robert Kidston 3 described an imper- 

 fectly preserved specimen showing what appeared to be stalked syn- 

 angia or quadrivalvate capsules in union with Neuropteris hctcro- 

 phylla. The pteridophytic nature of this fructification has been 

 generally unquestioned, although, on the evidence of the relation 

 of the fronds to Medullosa, the genus Neuroptcris has been put with 

 the Cycadofilices by many authors. The recent discovery by the 

 same distinguished paleobotanist 4 of large solitary Rhabdocarpous 

 seeds attached to the fronds of the same species of Neuropteris more 

 than confirms the exclusion of these anomalous types from the ferns. 



1 Comptes Rendus, vol. 94, 1882, p. 1737. 



2 It is of interest to note, in this connection, that in the Lacoe fossil plant 

 collection of the U. S. National Museum one of the rock slabs, about no 

 cm. long and 55 cm. in width, contains a fragment from the interior of a 

 frond of Alethoptcris aquilina in which a rachis 3 cm. or more in width, 

 lying near the border of the slab, gives off 6 alternate primary pinnae, none 

 of which is small enough to be included in its entirety within the area of the 

 rock, while in the longest fragments of pinna;, 65 cm. to the broken end, 

 there is no diminution in width. It is impossible to say how high the whole 

 segment may have been above the lowest primary pinnae; but since none of 

 the pinnules of the secondary pinnae is even lobed it is evident that the speci- 

 men comes from the upper part of the frond. Doctor Scott (Phil. Trans. 

 vol. 191B, 1899, pi. ix) figures a flattened petiolar base of Medullosa that is 

 nearly 9 cm. in width. 



"Trans. Roy. Soc. Edinb., vol. xxxiii, pt. 1, p. 150. 



* Proc. Roy. Soc, vol. lxxii, Dec. 29, 1903, p. 487; Trans., vol. 197E, 1904, 

 p. 1. 



