684 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
roots are grouped in tufts, which arise at, or immediately above, the nodes, and close 
to the insertion of lateral branches.* 
Srur, in his account of the roots of Calamites, mentions one point of considerable 
interest.t He finds that the woody cylinder of the root is not always median, but is 
often laterally displaced, showing that it was freely movable within the outer cortical 
envelope. This fact finds its explanation now that we know that the middle cortex 
of Calamitean roots was traversed by large lacunz, and would thus offer little resist- 
ance to the displacement of the central cylinder. 
StuR mentions that some of the roots observed by him bear rootlets, while others 
do not. He is disposed to regard the latter as floating roots, the former as having 
grown in the soil. 
A fine specimen of a Calamitean stem, showing clearly the insertion of the roots 
exactly on the nodes, has been figured by RENavtrt.} 
From the sources mentioned, as well as from others, we thus have a general idea of 
the external characters of the adventitious roots of Calamites, and of their arrange- 
ment on the stem. It is only quite recently, however, that we have acquired any 
exact knowledge of their structure. As mentioned in our former paper,§ RenavuLt 
has now found decisive proof that certain fossils formerly described under the name 
of Astromyelon|| are identical with the roots of Calamites, thus confirming the 
conclusion at which he had already arrived in the year 1885." 
Relation of Root and Stem. 
The evidence for the fact that roots with the structure of Astromyelon were borne 
on Calamitean stems, depends at present on the discoveries of RENAULT, who in 
his latest work repeatedly figures such roots in direct connection with the stem of 
his Arthropitys (our Calamites) as well as of Calamodendron and Bornia.** 
* See Part IT., Plate 8, fig. 1, and Plate 9, fig. 1. 
+ D. Srur, ‘‘ Die Calamarien der Carbon-Flora der Schatzlarer Schichten,” 1887, p.1; published in 
* Abhandlungen der Kaiserlich-K6niglichen Geologischen Reichsanstalt.’ Vienna. 
{ Renavtt et Zeruier, ‘ Flore houilliére de Commentry,’ Part II., Plate 57, fig. 1. 
§ Wituramson and Scort, “ Further Observations on the Organization of the Fossil Plants of the 
Coal-Measures,” Part I., p. 899, ‘Phil. Trans.,’ B., 1894. 
|| Wittramson, * Organization,” Part IX., 1878, p. 319; Part XII., 1883, p. 459. Hick and Casu, 
“Flora of the Lower Coal-Measures of Halifax,” Part TII., 1881, and Part IV., 1884; published in 
‘Proc. Yorkshire Geological and Polytechnic Society,’ vols. 7 and 8. Their specimens are named by 
them Myriophylloides ; the question of the identification of the latter with Astromyelon will be considered 
below. See also Renautt, “Végétaux fossiles du genre Astromyelon,” ‘Ann. des Sci. Géol.,’ vol. 17, 1885. 
{ ‘‘ Nouvelles Recherches sur le genre Astromyelon,” ‘Mém. de la Soc. des Sci. Nat. de Saéne et 
Loire,’ 1885. 
** Renautt, “Flore fossile du bassin houillier et permien d’Autun et d’Epinac,” Part IL., 1894; 
published in ‘Etudes des Gites Minéraux de la France.’ See especially Plates 42, 43, 44, 53, 54, 55, 59. 
The text of this memoir has not yet appeared. 
