ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 685 
Among our own specimens, which RENAULT regards as specifically distinct from 
his own, such evidence is scanty. In one case, however, we believe that the 
connection between root and stem is distinctly shown. The sections numbered 
C.N. 13851—C.N. 1355 (see Plate 15, photographs 1 and 2), in the Witttamson Collec- 
tion, were all cut from the same specimen. They are all approximately tangential 
sections of the wood of a main axis, on which lateral roots* are borne. Three of 
these roots are cut through transversely on their way out through the wood. 
Two of them are placed side by side, and appear in the same section (C.N. 1355). 
All three exhibit the typical structure of the larger specimens of Astromyelon—a 
considerable pith (which has been bored by Stigmarian rootlets, but was probably 
solid in life), a ring of centripetal xylem-groups (10 to 12 in number), and a zone of 
secondary wood, which is connected with that of the parent axis (see photograph 1). 
There can bé no doubt that the specimen shows the attachment of the roots to a main 
axis of some kind. The question to be solved is, whether this main axis was itself a 
root ora stem. This question appears to be decided by one of the sections (C.N. 
1353; see Photograph 2), which distinctly shows three of those “lenticular organs,” 
or enlarged medullary rays, which are so characteristic of the stem of Calamites, in 
its infranodal regions, but which, so far as we know, are entirely absent from the 
roots themselves.t At two points, also, the transverse sections of outgoing leaf-trace 
bundles can be distinguished. Photograph 2 shows one of the “lenticular organs,” 
and one of the leaf-traces, which is especially clear. These facts demonstrate that 
the section passes through a node, and therefore that the axis is a stem. ‘This 
conclusion is further strengthened by the fact that immediately above the node we 
find the base of a branch (probably abortive) which is thus in the normal position for 
branches of the stem of Calamites.{ 
This specimen may therefore safely be regarded as affording additional evidence 
that organs with “ Astromyelon”’ structure, were borne on Calamitean stems. 
The nature of the organs hitherto known under the name of Astromyelon, is now 
so far established that we know them to have been appendages of the stem of 
Calamites (Arthropitys of the French authors). Renautr has shown that very 
similar appendages, also showing the Astromyelon type of structure, were produced 
on the stems of Bornia and Calamodendron.§§ So far as our English specimens of 
‘“ Astromyelon” are concerned, we have no reason to doubt that they all belonged to 
the genus Calamites, though it is very probable that various species may be 
represented among them. The direct evidence of continuity applies only to the larger 
specimens, such as those originally described, in which there is a conspicuous pith.|| 
* The proof that these organs are, morphologically, roots, will be fully given below. 
+ See our previous memoir, ‘‘ Further Observations,” &c., Part I., p. 887; also WuituiaMson, 
“Organization,” Part [X., p. 325. 
t See our “ Further Observations,” Part I., pp. 890 and 893. 
§ Loc. cit., “ Flore fossile d’Autun,” Part II., Plates 42 and 43, 59 and 60. 
|| See Wiiutamson, “ Organization,” Part 1X , Plate 19, figs. 1-7. 
