492 
PKOFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
Hitherto nearly all phytologists, with the exception of Mr. Binney ancl Mr. Carruthers, 
have endeavoured to infer the structure of Calamites from the appearances presented by 
specimens from which all structure has disappeared. A comparison of their inferences 
with what are now positively ascertained facts, demonstrates the danger of this mode of 
procedure, and confirms an opinion I have elsewhere expressed, that no determinations 
respecting fossil plants can have much absolute value save such as rest upon internal 
organization ; that is the basis upon which all scientific recent botany rests, and no mere 
external appearances can outweigh the positive testimony of organization in fossil types. 
But whilst thus insisting upon the supreme value of structure as a guide, I am not blind 
to the importance of a mass of evidence that has been derived from the study of external 
forms, and especially that for which we are indebted to my two friends, Dr. Dawson, of 
Montreal, and M. Grand’ Eury, of Saint Etienne, in France. Whilst many of the spe» 
cimens which I have described have unquestionably been aerial stems , the minute size 
of others makes it exceedingly probable that they were small branches ; nevertheless 
there is no variation in the structure of these two classes of organs, beyond what has 
arisen from the gradual absorption of the pith as the plant increased in age. But we 
have in this difference the first clue to the history of the common fossil forms. It has 
often been observed that very small Calamites were exceedingly rare, leading to innu- 
merable surmises as to the cause of this fact. 
The specimens of Calamites usually seen are casts of the interior of the wood-cylinder 
of the stem, either composed of sandstone or of shale, and are generally covered with a 
thin homogeneous layer of carbonaceous matter. The early writers almost invariably 
turned these specimens upside down, believing their obtuse or conical bases to be the 
uppermost extremities of the stems. These observers experienced further difficulties in 
the circumstance that whilst the internal casts were fluted longitudinally and marked at 
intervals by transverse constrictions, similar features were exhibited, more or less strongly, 
by the external surface of the carbonaceous covering of each specimen. Hence the 
apparent probability naturally suggested itself, that in the living plant one calamitean 
structure had existed in the interior of another. But it was invariably believed that the 
internal Calamite represented a solid pith that had disappeared from the inorganic decom- 
position of its tissues after death, the place of the lost tissue having been supplied by 
sand or mud, according to the nature of the sediment under which the plant became 
buried. At an early period of my recent observations X became satisfied that the living 
plant had possessed a fistular medulla, and M. Grand’ Eury, studying a very different 
class of specimens to mine, arrived at the same conclusion*. 
* Observations snr les Calamites et les Asterophyllites, par M. Grand’ Eury, Comptes Rendus, tom. lxviii. 
p. 705. That author correctly says, “ la presence frequente aux jointures de cloisons plus ou moins entieres est 
une evidence complete que ces tiges etaient fistuleuses.” But in his definition of the genus Calamites, and in 
many of his general observations embodied in the same memoir, this careful observer has been seriously but 
almost inevitably misled, arriving at several conclusions diametrically opposed to the demonstrations which my 
better preserved specimens have afforded. 
