or THE FOSSIL PLANTS OF THE COAL-MEASUEES. 
225 
recognized views as to the relations of scalariform to discigerous tissue that it failed to 
meet with acceptance. The chief difficulty which stood in the way of my adopting it 
was the entire absence from our British deposits, in which structureless Sigillarice are 
so common, of any stems with a structure corresponding to it ; but it must be admitted 
that, as yet, I have obtained no trustworthy specimens which I could, without possibility 
of doubt, affirm to be the true vascular axes of Sigillarice. Portions of the bark are, as 
I have shown in one of my previous memoirs, sufficiently common, whilst decorticated 
vascular axes of Diploxyloid types are also far from rare ; and seeing that many of these 
latter approach so near to the Sigillarian stem figured by Brongniart as well as, in all 
essential features, to that of Sigillaria spinulosa described by MM. Renault and 
Grand’ Eury*, it appeared to me extremely probable that some of these Diploxyloid 
axes belong to true Sigillarice. In no one of these have we found a trace either of a 
Sternbergian pith or of the discigerous fibres in the exterior of the vascular axis which 
Dr. Dawson has described as existing in his American examples. Nevertheless we 
must not conclude from this that Dr. Dawson is in error, either in the accuracy of his 
description or in his belief that the stems described are those of true Sigillarice , even 
though we may be convinced that these plants are Cryptogams and not Gymnosperms, 
as Dr. Dawson thinks probable f. That Sternbergian piths may occur in Lycopods, as 
well as elsewhere, is shown in the case of Corda’s Lomatophloios crassicaule ; and, if 
Sachs is right in his explanation of the real structure and origin of the bordered disks 
of coniferous fibres, there is no morphological or physiological reason why the barred 
vessels forming the inner zones of the axis of a Lepidodendroid plant should not gra- 
dually change towards its periphery, first into what Dr. Dawson terms pseudo-scalariform 
tissues, and still more externally into discigerous ones. But even admitting all this to 
be true in the fullest sense that Dr. Dawson would demand, it does not bring me one 
bit nearer to the admission of Sigillarice amongst Gymnospermous plants, or to their 
separation from the Lepidodendra. With the bark of our common ribbed Lancashire 
Sigillarice we are now thoroughly familiar, and its very remarkable structure is as 
identical with that of the Lepidodendra as it can possibly be, whilst it is as different 
as possible from any known Gymnosperms, recent or fossil. In one of his latest popular 
works, speaking of Sigillarice, Dr. Dawson says, “ Some regard it as a Gymnosperm, 
others as a Cryptogam. Most probably we have under this name trees allied in part 
to both groups, and which, when better known, may bridge over the interval between 
them”J. Dr. Dawson has recently forwarded to me his latest definition of Sigillaria, 
with permission to make use of it. It is as follows ! — 
* Memoires presentes par divers Savants a l’Academie des Sciences de l’lnstitut National de France, 
tome xxii. no. 9. 
t In a letter to the author, dated April 14, 1876, Dr. Dawson says, “ I have never held that any Sigillarice 
are Conifers, but only that some Sigillarice in their tissues closely resembled the Cycads and were Gymnosperms. 
I have also held, on the evidence of form of scar and leaf, that some so-called Sigillarice , especially those of the 
Clathraria type, are of humbler structure and allied to Lycopods.” 
t ‘ The Story of the Earth and Man,’ p. 124. 
