August 20, 1885] 
NATURE 
365 
plants I found numerous statements with which I could not 
agree. Some of these statements refer to questions of facts ; 
others to inferences drawn from real or imaginary facts. Having 
long enjoyed the valued privilege of a correspondence with my 
distinguished friend I sent to him a lengthy criticism of parts of his 
new volume which I thought to be seriously misleading ; either 
because matters of fact were so exhibited as to convey erroneous 
impressions, and hence, practically, to become not facts—or 
because they were made to justify conclusions which the 
facts themselves, rightly stated, would not do. At the same 
time I gave my correspondent warning that I might have to 
correct what I regarded as his erroneous or misleading 
statements. 
Mr. Gardner’s article leads me to fulfil this “announcement 
sooner than I intended, since he, in turn, has so far countenanced 
some of what I regard as the errors of the two French palzeonto- 
logists as to make them his own. Like Mr. Gardner, M. 
Saporta had previously pointed out to me that the aim and 
object of his volumes did not necessarily involve interference 
with matters that have so long been in dispute between M. 
Rénault, M. Grand’-Eury, and myself. To this I could only 
reply that in his new work he had repeatedly shown his ac- 
ceptance of views of these two paleontologists involving 
both facts and inferences, which I believe to be seriously 
erroneous. The space which NATURE can afford me will not 
suffice fully to review all of what I regard as the objectionable parts 
of the two volumes under consideration, but I may be allowed 
to make some comments, including some extracts from my letter 
to M. Saporta, indicating the nature of my objections both to 
his conclusions and to the comments made upon them by 
Mr. Gardner. 
The latter gentleman makes one statement which I cannot 
endorse. Because MM. Rénault, Grand’-Eury, and Saporta all 
adopt the views of M. Brongniart he thinks it hardly possible that 
they can all be mistaken. This argument cuts both ways— 
Mr. Gardner applies it to the subject of Calamites versus Cala- 
madendron. On this subject I may retort that when such men 
as Schimper, Weiss, Stur, and perhaps my prolonged investiga- 
tion of the subject justifies my adding myself, take an opposite 
view of the matter in debate, it may possibly be equally im- 
possible that we, with our vast array of specimens in our 
cabinets, should all be mistaken! This a7gumentum ad hominem 
therefore falls to the ground. I may be allowed to wonder that 
it should ever have been advanced. 
The first point to which I would call attention shows that 
such men as those quoted may blunder and have blundered. 
I now refer to the subject of the relations of Lepidodendron 
and Sigillaria to each other and to the rest of the plant world. 
That I have for many years insisted upon the cryptogamic 
character of, and the close affinity existing between, both these | 
genera is well known ; and equally so, that many of the French 
paleontologists have followed M. A. Brongniart in regarding 
the Lepidodendra as Lycopodiaceous plants whose stems con- 
tain no exogenous vascular cylinder, whilst all those plants that 
possessed such a cylinder (a product of a Cambium layer) which 
they believed to be the case with Sigillarize must, de facto, be 
Gymnosperms. That this dispute has now been settled in my 
favour by an important recent discovery does not seem to be 
known to Mr. Gardner. M. Zeiller has obtained strobili of Sigil- 
laria which have settled the matter even in the opinion of most 
of the Parisian botanists. Those strobili contain spores, not 
seeds. This discovery demonstrates the cryptogamic character 
of Sigillaria, and deals a final blow at the Gymnospermous 
hypothesis held by the four observers in whose combined in- 
fallibility Mr. Gardner expresses such confidence. 
My first friendly complaint against the authors of the 
** Evolution of the Phanerogams” is that they disregard proven 
facts when such facts inconyeniently oppose their theories. 
Imprimis, they became aware of M. Zeiller’s important dis- 
covery whilst their volumes were passing through the Press. 
Though this is a sufficient reason for only noticing it in a foot- 
note, it does not justify their very slight recognition of its bearing 
upon so many pages of their arguments, of which it effectually 
disposes. It absolutely establishes the fact that some Sigillariz, 
at least, are of Gymnosperms but Cryptogams ; which fact, 
superadded to the many identities of structure in Sigillaria and 
Lepidodendron, which I have repeatedly shown to exist, 
renders it increasingly probable that the above statement is 
applicable to a// Sigillariz. At least, it now throws upon the 
opponents of that statement the onus of proving the contrary 
to be true, which they have not done. 
Several years ago the late Mr. Binney described what he 
believed to be two plants—the Lepidodendron vasculare and the 
Sigillaria vascularis. That the only difference between these 
two was the possession, by the latter, of an exogenous zone, not 
seen in the former, was recognised by Mr. Binney. I have 
shown in a way, which I claim to he unanswerable, that these 
are one and the same plant which the external and internal 
characteristics alike demonstrate to be a Lepidodendron. 
Hence I complain to M. Saporta, ‘‘ You continue to speak of 
Sigillaria vascularis. I reply that there is no such plant; and 
to speak of the Lefzdodendron under that name, after all that 
I have done in illustration of its organisation, is unfair to me, 
besides seeming to support M. Rénault’s absurd conclusion that 
an exogenous or centrifugal zone is incompatible with the 
possibility of a plant possessing such a zone being a Lepido- 
dendron.” I then state ‘‘further, after enumerating M. 
Rénault’s three supposed types of Lepidodendron, from which 
he excludes all possibility of the existence of an exogenous zone, 
you say, ‘ce sont les traits essevtiels des types caulinaires 
Lepidodendroides.’ 
“*T reply in language as strong as I can possibly use that this 
is not true. The development of an exogenous zone in the 
more advanced stages of a Lepidodendron’s life is the rule 
rather than the exception.” 
After citing numerous proofs of this statement I say in 
reference to Sigillaria: ‘‘It is further a mistake to say that 
“ces tiges nous sont principalement connues par les Sigillaria 
elegans et spinulosa.” We possess the vascular axis of the 
Sigillaria figured in my Memoir II., Fig. 39. This axis is 
identical in the minutest details of its organisation with those of 
the Diploxyloid Lepidodendra, and I have sections of Sigillaria 
reniformis which are, in structure, equally Lepidodendroid, 
I ask, therefore, what are the ‘diversités appréciables’ to 
what you refer on p. 23, and what ground have you for saying 
that this double fibro-ligneous region is ‘sans analogie avec 
ce qui existe dans les tiges connues des Lepidodendrées ’?”” 
On this part of the disputed questions I must object to a 
statement made by Mr. Gardner, in which he says that the 
structure of Lepidodendron ‘‘ presents nothing unusual to 
Cryptogams.” Surely a thick exogenously developed cylinder of 
scalariform vessels, arranged in radiating laminz, separated by 
true medullary rays, the entire structure being produced by a 
Cambium zone, is very unusual in Cryptogams. Mr. Gardner 
then proceeds, as M. Saporta would do, to describe a contrast 
which has no real existence. ‘But in Sigillaria, a plant 
strongly resembling it in nearly every other respect, we find a 
radiating vascular or woody zone in the cellular stem with 
unmistakable exogenous growth. It is richly supplied with 
medullary rays, and, Prof. Williamson allows, presents clear 
evidence of interruptions to growth succeeded by periods of 
renewed vital activity.” I allow, and never have allowed 
anything of the kind,1 if this means my admission that some- 
thing exists in Sigillaria that does not exist in most Lepido- 
dendra. Mr. Gardner further represents me as believing that 
‘the typical Lepidodendron never produced a ligneous zone.” I 
believe the reverse of this ; viz. that a development of such a zone 
sooner or later was characteristic of most Lepidodendra. True 
there are some Lepidodendra in which I have not yet discovered 
such a zone; but I am far from supposing that even in them 
such a zone will not ultimately be discovered. Anyhow the 
typical Lepidodendron can no longer be regarded as one from 
which this zone is absent. Mr. Gardner, after the passages 
quoted above, says: ‘‘In Diploxylon there is a further de- 
velopment, the woody zone being made up of an inner or 
medullary vascular cylinder either interrupted or continuous, 
composed of large scalariform vessels without definite order, and 
an outer cylinder of scalariform vessels of smaller size arranged 
in radiating fasciculi.” What does this “ further development ” 
mean? This description is simply that of every exogenous 
Lycopodiaceous axis found in the coal measures, whether of 
Lepidodendron or of Sigillaria. Diploxylon, as a genus, has no 
longer any existence. The term is now useful only as an 
adjective descriptive of a condition of growth common alike to 
Lepidodendron and to Sigillaria, as well as to several other 
genera of Carboniferous plants. Unless I misunderstand Mr. 
1 I may here observe that conspicuous or even visible interruptions to 
growth are very rare amongst these coal plants. They are only very 
conspicuous in my genus Amyelon; but we also find traces of them in 
Stigmarian roots and in Lygenodendron. Generally these Carboniferous 
stems suggest the reverse of changing seasons or periodic interruptions 
of growth. 
