528 
Note . 
consists in the appearance of a cambium at the periphery of the pith, 
forming medullary wood and bast, with inverted orientation. This 
is precisely the anomaly shown by certain species of Tecoma , and 
other dicotyledons. The anomalous medullary cambium is con- 
tinuous with the normal cambium through the leaf-trace gaps. This 
case is a striking instance of the independent appearance of the same 
structural peculiarity in families as remote as possible from each 
other. 
B . The Leaf. 
1. Connexion between Leaf and Stem. — New and conclusive evidence 
has been found, confirming the conclusion previously arrived at (in 
Mem. XVII), that 1 Rachiopteris aspera’ is the petiole of Lygino- 
dendron. In several specimens petioles with the characteristic struc- 
ture of that fossil are found inserted on the stems of Lyginodendron. 
The vascular bundles on leaving the pericycle of the stem bend out 
rapidly into the base of the leaf, becoming concentric at the same 
time. Petioles, continuous with the Lyginodendron stem, have been 
traced up to the point where they begin to ramify. 
2. Form of the Leaf — The petioles, which we now know to belong 
to our plant, branch repeatedly, and ultimately give rise to small 
palmately-segmented leaflets. The leaf was thus a highly com- 
pound one, and we can confirm the statement previously made, 
that the character of the foliage was that of Brongniart’s form-genus 
Sphenopieris. 
3. Structure of the Petiole —The most important point here is that 
throughout the petiole and rachis, the vascular bundles, of which 
either one or two are present, are of typical concentric structure, as 
in a fern. 
The cortex of the petiole has essentially the same structure as that 
of the stem. 
4. Structure of the Lamina. — We have examined sections of leaflets 
(found in connexion with petioles of Lyginodendron ), in which the 
structure is perfectly preserved. The lamina had a distinctly bifacial 
structure, with well-differentiated palisade, and spongy parenchyma. 
Stomata have only been observed on the lower surface. The vascular 
bundles in the lamina appear to have been collateral, as is also the 
case in recent ferns. 
5. On a Peculiar Bud-like Structure . — This is a unique specimen, 
