420 MR. Je S. GARDNER ON ALNUS RICHARDSONI. 
attached. The pith-cavity of the stem, again, is almost always indi- 
cated in the fossil, and is marked by either a protuberance or depres- 
sion, its different texture causing it to decay unequally on exposure. 
A section made by Bowerbank shows it very clearly (fig. 22). 
The axis of the cone is cylindrical (fig. 21) or ovate (fig. 14), 
and is often exposed, and sometimes so completely denuded of 
scales as to have been described as a distinct fruit. It is covered 
with somewhat complex lozenge-shaped scars, marked out in part 
by the bases of the scales. The scars form depressed areas with 
raised margins and a central prominence or umbo, to which the 
seed was apparently socketed. The axis in Alnus is very similar 
externally, though the scars are rounded or pear-shaped ; but it 
differs structurally, for the scale springs from the centre of the 
depressed area, and the seeds have no appearance ot being socketed, 
but seem to have been produced on the raised and more pulpy 
margins of the scars. The scales of the cone are less pyritized 
than the interspaces, and have frequently decayed and left hollow 
spaces. Though these have been spoken of as cells with semi- 
circular mouths, there is not the least doubt that the cavities are 
actually due to the decay of lignitic matter (which has to a large 
extent replaced the woody tissue of the scales) being more rapid 
when exposed to sea- and atmospheric action, than the solid pyrites 
which has infiltrated between them. The lignite, in fact, still exists 
in many specimens (fig. 20), and may be picked out with aneedle, 
and one of the cavities thus immediately produced. The upper sur- 
face of the scale is hollowed and furrowed to receive and hold the 
seed, and the apophysis is thickened (fig. 20, a, 6), and apparently 
may have been crenulated. It is doubtful, however, whether the 
actual apex has not been more or less abraded in all the speci- 
mens. In Alnus glutinosa the scale divides, and is composed at 
the apex of a bundle of tissue forming a loosely crenulated 
head; but it does not appear that the fossil scale was similarly 
formed. When, however, melted wax is allowed to fill the inter- 
stices of the recent cone (fig. 13), the resemblance to the fossil 
is considerably enhanced; for the scales then assume a more 
regular and compact appearance, and the likeness is still further 
increased if the apices are sliced away with a sharp knife, their 
thin erescentic outline becoming identical with the fossil, except 
that the ends point slightly downward instead of upward (fig. 13, 
basal part). The seed (fig. 23) is solitary, and is found en- 
closed in the solid pyrites between the scales. It is pointed at 
