Notes. 
609 
Each leaf-trace springs from the small external elements of the 
xylem, and consists of six tracheae in the form of a tangentially 
extended group, and of six to eight radially disposed centripetal 
bands of scalariform tracheides, each band including four elements. 
The foliar bundles consist of primary xylem only, and follow a radial 
course through the medullary rays of the secondary wood. 
The secondary wood is twenty-three elements in thickness ; the arc 
opposite each sinus of the corona is composed of ten to twelve radial 
bands of tracheides, while the arc opposite a projecting tooth of the 
course includes four to six bands. There are thus thirty-two radial 
series of tracheides between two outgoing leaf-traces; the elements 
opposite the teeth are somewhat smaller in diameter than in the xylem 
opposite the sinuses, but the difference is very slight. 
In Sigillaria spinulosa from Autun the leaf-traces arise from the 
same point in the corona as in the ribbed stem from Haidinghen; 
their arrangement and the structure of the wood is also the same ; but 
in the former species the primary wood occurs in the form of distinct 
groups or islands occupying positions corresponding to the sinuses in 
the corona of the ribbed Sigillaria . In A. spinulosa there is no 
primary xylem in the positions corresponding to the teeth on the 
surface of the corona of the Haidinghen stem. The polar regions 
( c regions polaires ’), which tend to Be differentiated in the projecting 
teeth of the corona of the ribbed Sigillaria, are not represented in the 
corona of the Leiodermarian type of stem. Moreover, as Renault has 
stated, the leaf-traces of the latter type of Sigillaria consist in part 
of secondary xylem. The arrangement of the spiral elements is also 
different in the two species. In S. spinulosa there are ten to fourteen 
radial bands of secondary tracheides opposite each group of primary 
xylem, and four to six bands of smaller elements opposite each 
interval separating the detached groups of which the corona is 
composed. In the number (thirty-two to thirty-four) of radial series 
between two outgoing traces, the two species agree. We see, there- 
fore, that there is a close agreement in the structure of the Leiodermaria 
and Rhytidolepis types as regards the manner of exit of the leaf-traces; 
but the disposition of the small protoxylem-elements affords a striking 
distinction. In the Autun Sigillaria there is also a tendency to 
differentiate the secondary wood opposite the sinuses from that 
opposite the teeth. 
A comparison of the ribbed Sigillaria of Haidinghen, with the 
