﻿white] fossil plants of group cycadofilices 385 



Shale of Kentucky. The fronds and fructification of Calamopitys 

 arc unknown. 



The Cycadoxylece. — The stems published by Renault 1 as Cycad- 

 oxylon are still closer to the Cycads, and their secondary wood is 

 described as distinctly Cycadean. But the Cycadoxylon stem pre- 

 sents a strikingly anomalous feature in the occurrence, within the 

 cylinder of outer (normal) secondary wood, of two or more distinct 

 /.mies of inner crescentic secondary wood, each zone of which with its 

 rays and accompanying broad phloem bands, lies in an inverted 

 position in the body of the pith. The genetic connection with 

 Lyginopteris is shown not only in the general characters of the 

 centrifugal wood but also by a slight development of a similar 

 medullary secondary wood in certain specimens of the latter genus. 



An important link between the Lyginopterid group and the Cycad- 

 ales (in a broad sense) is furnished by the stems described by 

 Renault 2 as Ptychoxylon, another of the Cycadoxylese, which is 

 regarded by both its author and Doctor Scott as essentially Cycad- 

 aceous. In this genus (see plate liv, fig. 1) a very large pith is 

 surrounded by a more or less complete narrow zone of secondary 

 wood similar to that of the other stem genera. But within the 

 cylinder of normal centrifugal wood lie several concentric arcs of 

 fully developed inverted secondary wood, each with its phloem, 

 medullary rays, and phloem rays. At the leaf gaps the edges of the 

 interrupted outer or normal cylinder curve inward to coalesce tem- 

 porarily with two of the inner arcs of inverted exogenous wood, 

 which are termed " reparatory " arcs. In the relations of the nor- 

 mal and inverted secondary woods Ptychoxylon appears to present 

 some analogies with Colpoxylon and MeduUosa, No primary wood 

 appears yet to have been observed in the petrified stems, though the 

 leaf trace is said to be essentially like that of Lyginopteris. 



Except for the anomalous medullary wood Ptychoxylon is Cycad- 

 aceous ; and this systematic reference is supported by the discovery, 

 in the same beds, 3 of leaves (Ptcrophylluin and Sphenozamites) 

 which in form and external characters are distinctly Cycadean, ac- 

 companied by a remarkable inflorescence (Cycadospadix milleryensis 

 Ren.) provisionally referred to Ptychoxylon by Renault. 



Protopitys. — In Goeppert's Protopitys originally described from 

 the Lower Carboniferous of Silesia and more fully made known by 



1 Flore fossile dit bassin houill. ct permien d'Epinac, pt. 2, 1896, p. 307; Wil- 

 liamson, Phil. Trans., vol. 163, 1873, P- 377', Williamson and Scott, Phil. 

 Trans., vol. i86b, 1896. p. 703; Seward, Ann. hot., vol. xi, 1897, p. 65. 



2 Op. cit., p. 329. 



3 Loc. cit., p. 329. 



