79 
Knowledge oj Lyginodendron. 
the figures illustrating the structure of this Autun specimen 
with those of Lyginodendron robustum brings out a striking 
similarity as regards the structure of the centrifugal wood. 
The tangential section figured in PI. V, Fig. 7, of the present 
paper is very similar to the corresponding section of Cyca- 
doxylon (Renault, PL XIV, Fig. 12). There is also a close 
agreement between the transverse and radial sections of the 
wood of the two plants (cf. Renault, PL XIV, Figs. 10 and n,and 
Lyginodendron robustum , Figs. 4, 8 , 10, 16). More recently 
M. Renault has supplemented his earlier account of Cycadoxylon 
by additional figures and a further description published in 
an important work on the coal-field of Autun and Fpinac. 
The following description of the structure of the wood as 
seen in a transverse section of Cycadoxylon Fremyi illustrates 
the most striking characters : ‘ Le systeme ligneux est 
compose d’un cylindre exterieur continu d’arcs ligneux dis- 
perses dans la moelle en nombre variable. Le cylindre 
exterieur est forme de series rayonnantes de tracheides, ponc- 
tuees, a accroissement centrifuge ; les bandes ligneuses inte- 
rieures sont constitutes par des series rayonnantes semblables, 
mais dont Laccroissement est centripete ’ 1 . Renault compares 
this genus, of which Cycadoxylon Fremyi is the only example, 
with P tychoxylon and Medidlosa. The centrifugal and centripetal 
bands of xylem are separated from one another by parenchy- 
matous tissue, and there is no indication of any continuity 
between them in a radial direction, nor are there any groups of 
primary xylem internal to the centrifugal wood such as occur 
in Lyginodendron Oldhamium. Since writing this paragraph 
I have had an opportunity, through the kindness of M. Renault, 
of examining the sections of Cycadoxylon. In one specimen 
a small group of primary xylem was clearly shown. 
In Fig. 56 (p. 309)' of the Flore fossile d’Autun et 
d’Epinac, a portion of a transverse section of Cycadoxylon 
1 Bassin Houiller d’Autun et d’Epinac. Flore fossile, Pt. II, p. 307. I am 
indebted to M. Renault for kindly forwarding me a proof of that part of his 
forthcoming work which deals with Cycadoxylon. [The text of this work has now 
appeared. January, 1897.] 
