1899] ON THE ANATOMY OF FOSSIL J 'LA NTS 369 



1 by their endogenous origin ; tangential sections through the 

 of the parent plant, and passing also through an adventitious root, 

 snowing the latter as a complete organ | g a cortex and 



epidermis of its own, whereas a similai ection through the base of a 

 branch would show only the vascular tissi og outwards from the 



le of the main stem. The authors point out that — "The typical 

 root-; of Lyginodend/ron, before the commencement of secondary growth, 

 often beaT a strikii mblance to the smaller roots of recent 



Marattiaceae." ' 



The roots exhibit secondary thickening in a quite normal manner, 

 but curiously enough become more like certain dicotyledonoi 



Cucurbita /'</«>> than those of cycads or ferns. The peculiar and 

 characteristic appearance presented by the older roots, in which the 



indary xylem shows a peculiar disposition, generally into five or six 

 large wedges, separated from one another by wide parenchymatous 

 wedges, is simply due, as also in the Cucurbita mention';'! above and 

 figured by De Bary, 2 to the fact that, whereas opposite the primary 

 phloem groups great masses of xylem separated by narrow medullary 

 formed, thus building up the wedges of wood, opposite the 

 primary xylem the cambium forms mainly parenchyma. 



All the specimens of Lygmodendron, of which the structure is 

 described by Williamson and Scott, are comparatively small in -./•• 

 (no! ling about 4 cms. in diameter), while many of the 



bical impressions, if they really belong to Lyginodendi'on, represent 

 plants which must have attained the dimension of trees. Mr. 

 A. C. Seward 1 ribed, under the name of L. rdbudumf the 



structure of a much larger specimen, of which the diameter of the 



»dy cylinder and pith alone attains 14 cms. The preservation of 

 this specimen is not as good as in L. Oldhamium (the ordinary form;, 

 but traces of the primary bundles can be 1 an internal ring 



of centripetal xylem, similar to what has been described in L. Old- 

 hamium as anomalous wood. The author points out that there is 

 great similarity between L. rdbudum and a type from Autun, described 

 in 1870 by Renault as Cycadoxylon Fremyi, and adds that "the term 

 Cycadoxylon proposed by Renault, if extended in its application, might 

 .. general generic designation for plants | condary 



xylem closely resembling that of recent Cycads." 4 



In tie: 1 Permo-carboniferous PoroxyUm described by MM. 



Bertrand mid Renault/ we find a similar arrangement of parte to that 

 in Lygmodendron. They too must have formed small trees. As in 



1 " Farther Observations," etc. Part. Ill- p 



- "' ; Anatomy of the Pha ., " English Edition, p. 174, 



fig. 201. 



'. Contribution to our knowledge of Lyginodendron," Annul-, >>r /;■•■ 



• !.<»■. eU., p. 84. 



I' oxylons," Arch. hot. du NorddU la I 1886. 



