890 PROFESSOR W. 0. WILLIAMSON AND DR. D. H. SCOTT ON THE 
Tut BRANCHING OF CALAMITES. 
Many of the specimens investigated show the insertion of lateral branches upon a 
relatively main axis.* In the great majority of these instances the branches are of 
small diameter compared with the stem which bears them. In judging of the 
relative dimensions, however, caution is necessary, for we know that in many cases 
the pith of the branch tapered almost to a point towards its insertion, giving rise to 
the well-known conical terminations of many of the medullary casts (see the figures 
in Plate 86). But, making due allowance for this fact, there can still be no 
doubt of the relatively small size of the lateral branches in very many cases, 
especially in those where several were given off at the same node. As already stated, 
the branches are always inserted immediately above a node, and are nearly always 
placed between two of the outgoing foliar bundles (see Plate 72, photographs 5 and 6 ; 
Plate 80, fig. 21; also Wint1aMson, “ Organization,” Part IX., Plate 21, fig. 28, where 
m indicates the foliar bundles).+ An exception is presented in a section of 
Calamopitus, in which a branch appears to be inserted immediately above one of 
the bundles, and in one case, so far as we have observed, in the typical Calamites.§ 
The branches often have a verticiliate arrangement, but do not seem to have been 
disposed in the whorl with any great regularity. Thus the transverse sections of one 
of the largest stems showing structure,|| pass through four lateral branches at the 
same node, which are placed at irregular intervals. Sometimes a single branch only 
was developed at a node, as is very clearly shown in the specimen? from which 
fig. 20, on Plate 79, is drawn. On the other hand a tangential section of a large stem 
shows four branches, regularly arranged at the same node, and suggests that here the 
whorl (of which such a section can only show a small part) may have been complete. 
Two of the four branches are shown in photograph 5, on Plate 72. 
The structure of the branch at or near its insertion is very clearly shown in a 
number of preparations (see Plate 72, photographs 5 and 6 ; Plate 79, fig. 20; Plate 80, 
figs. 21 and 22). Tangential sections through the inner part of the wood of the 
main stem show the basal portion of the branch in transverse section. In such 
preparations** we see that the branch has a parenchymatous pith, often completely 
preserved, sometimes partly fistular. Surrounding the pith we find a ring of xylem, 
arranged in more or less distinct bundles, which, though less obvious than those of an 
ordinary free stem, are still quite indubitable in good sections. That in these bundles 
* See the descriptions and figures in former Memoirs; Witu1amson, “ Organization,” Parts I. and IX. 
+ Also well shown in C.N. 20s, 90, 138*, &e. 
t See Wiuiamsoy, “ Organization,” Part I., Plate 28, fig. 38. 
§ C.N. 1937. 
|| C.N. 133*, 134*, &c. From 134* the fig. 22 on Plate 80 is taken. 
q ON. 132**. 
** As in C.N. 208, 90, 138*, besides those figured ; see also Winttamson, “ Organization,” Part IX,, 
Plate 21, fig. 28, 
