ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 725 
B.—Tue Luar. 
1. Connection between Leaf and Stem. 
The history of our knowledge of the leaves of Lyginodendron Oldhamium is briefly 
as follows : In Memoir IV. (1872) the opinion was already expressed that the “small 
stems or petioles” to which the provisional name of Hdraaxylon had been given, 
might probably prove to belong to Lyginodendron (loc. cit., p. 403). In Memoir VI, 
the specimens first named Edraxylon are fully described, and are incorporated in the 
provisional genus Rachiopteris (founded for the reception of fossil fern-petioles) under 
the name of R. aspera. The structure is fully described, and the discovery of leaflets 
in connection with the branched petiole, led to the conclusion that the leat’ belonged 
to Bronenrart’s genus, Sphenopteris. The species S. Haninghausi, which agrees 
with R. aspera in possessing a tuberculated rachis, was specially suggested for 
comparison. 
At a later period * the conclusion “ that Rachiopteris aspera is merely the petiole 
of Lyginodendron Oldhamium”+t was definitely stated, and proved by specimens 
in which the base of the petiole was found in actual connection with the stem, as 
well as by the presence of ideutical cortical outgrowths on both organs. 
It only remains for us to call attention to some additional specimens, in which 
the connection between leaf and stem is still more manifest. Two of these new 
specimens have been figured. 
Photographs 3 and 8 and fig. 10 (Plates 18, 19, and 23) are from the same specimen, 
of which we have four transverse sections.{ The order of the sections illustrated, 
from below upwards, is photograph 3, fig. 10, photograph 84. In all the sections 
figured the petiole is in manifest continuity with the stem, and, at the same time, 
it already presents the characteristic structure of Rachiopteris aspera. Other 
sections show the same petiole after it has become free; thus, fig. 11 represents 
the upper part of the same petiole in longitudinal section, at a point where it is 
beginning to branch. This figure shows several of the characteristic cortical emer- 
gences, thus affording the direct proof that Rachiopteris aspera, the only known 
Rachiopteris that possesses these outgrowths, was the petiole of Lyginodendron. 
Photograph 4, from another specimen, shows a radial section through a stem 
bearing a petiole. Both are in admirable preservation, so that all the details of the 
leaf-base can be made out. We also have series of sections from two other specimens, 
showing the connection between stem and petiole, and also the structure of the 
* See Wittiamson, Part XVII., 1890. 
+ Loc. cit., p. 91. 
t O.N. 1980 and 1981, and two sections in the possession of D. H. Scorr. All these were cut by 
Mr. Lomax, as well as those mentioned in the next foot-note. Other slides belonging to these series are 
in the Botanical Collections of the Royal College of Science, London. 
