TRANSACTIONS OF SECTION C. 487 
the earliest of known Conifers, belonged to the Taainee, the lowest of these coni- 
ferous types, and of which the living Sal¢sbwria may perhaps be regarded as the least 
advanced form. 
Thus far our attention has been directed only to plants whose affinities have 
been ascertained with such a degree of probability as to make them available 
witnesses, so far as they go, when the question of vegetable evolution is sub 
judice. But there remain others, and probably equally important ones, respecting 
which we have yet much to learn. In most cases we have only met with detached 
portions of these plants, such as stems or reproductive structures, neither of 
which are we able to connect with their other organs.. The minute tissues of 
these plants are preserved in an exquisite degree of perfection; hence we can 
affirm that, whatever they may be, they differ widely from every living type that 
we are acquainted with. The exogenous stems or branches from Oldham and 
Halifax which I described under the name of Astromyelon,! and of which a much 
fuller description will be found in my forthcoming Memoir xii., belong to a 
plant of this description, The remarkable conformation of its bark obviously 
indicates a plant of more or less aquatic habits, since it closely resembles those 
of Myriophyllum, Marsilea, and a number of other aquatic plants belonging to 
various classes. But its general features suggest nearer affinities to the latter 
genus than to any other, Another very characteristic stem is the Heterangium 
Grievii,? only found in any quantity at Burntisland, but of which we have recently 
obtained one or two small specimens at Halifax. This plant displays an abun- 
dant supply of primary, isolated, vascular bundles, surrounded by a very feeble 
development of secondary vascular tissue. Still more remarkable is the Zy- 
ginodendron Oldhamium,*? a stem not uncommon at Oldham, and occasionally 
found at Halifax. Unlike the Heteranyiwm, its primary vascular elements are 
feeble, but its tendency to develope secondary zylem is very characteristic of the 
plant. An equally peculiar feature is seen in the outermost layer of its cellular 
bark, which is intersected by innumerable longitudinal lamine of prosenchy- 
matous tissue, arranged in precisely the same way as is the hard bast in the 
Lime and similar trees, affording another example of the introduction into the 
outer bark of the appareil de soutien. As might have. been anticipated from this 
addition to the bark, this plant attained arborescent dimensions, very large frag- 
ments of sandstone casts of the exterior surface of its bark + being very abundant in 
most of the leading English coal-fields. Corda also figured such a cast * from Radnitz, 
confounding it, however, with his Lepidodendroid Sagenaria fusiformis, with which 
it has no true affinity. Of the smaller plants of which we know the structure but 
not the systematic position, I may mention the beautiful little Kalorylons.6 We 
have also obtained a remarkable series of small spherical bodies, to which I have 
given the provisional generic name of Sporocarpon.?’ Their external wall is multi- 
cellular; hence they cannot be spores. Becoming filled with free cells, which 
display various stages of development as they advance to maturity, we may infer 
that they are reproductive structures. Dr. Dawson has recently supplied me with 
some similar bodies, also containing cells, from the Devonian beds of North 
and South America. Except in calling attention to some slight resemblance exist- 
ing between my objects and the sporangiocarps of Pilularia,’ I have formed no 
opinion respecting their nature. Dr. Dawson has pointed out that his speci- 
mens also are suggestive of relations with the Rhizocarpe. 
T am unwilling to close this address without making a brief reference to the 
bearing of our subject upon the question of evolution. Various attempts have 
} Memoir ix.,in which I only described decorticated specimens. Messrs. Cash and 
Hick described a specimen in which the peculiar bark was preserved under the name 
of Astromyelon Williamsonis, See Proceedings of the Yorkshire Polytechnic Society, 
vol. vii. part iv. 1881. 
2 Memoir iii. 3 Memoir iii. 
4 Memoir iv. Pl. xxvii. 5 Flora der Vorvelt, tab. 6, fig. 4. 
§ Memoir vii. 7 Memoirs ix. x. 
§ Memoir ix. p. 348. 
