178 



EDWARD C. JEFFREY ON 



ured here, since the attached leaves are obviously situated in some cases immediately 

 above the scars of the branches, he abandons that position, and assumes the presence of 

 an intercalated node corresponding- to the crescentic series of smaller scars on the lower 

 margins of the branch-scars. The writer suggests that the crescentic rows of scars of the 

 figure, copied in photograph G (PL 30, fig. G), really belong to the basal whorls or ochre- 

 olae of the fallen branches and that as a consequence, so far as can be judged from exter- 

 nal appearances, the branches of Calamites had the same relation to the node as those of 

 Equiseta. The ochreolae of the Calamites were not continuous sheaths as in Equisetmn 

 but were composed of separate leaves. The ochreolae of the Equiseta not infrequently 

 lack fibrovascular bundles and are often obsolete on the upper axial side of the branch. 

 The occurrence of similar features in the Calamites is not improbable and these would 

 account for the absence of leaf-scars on the upper margin of the branch-scars and for the 

 non-retention of the ochreolar leaves, together with the normal leaves of the nodes of the 

 parent axis in photograph G (PI. 30, fig. 6). 



But without attaching too much importance to the above explanation, it will be well 

 to consider the internal relations of the branches to the nodes, as described in recent works 

 on calamitean anatomy, and, at the same time, to examine the statements as to the nature 

 and disposition of the organs which gave rise to the intranodal tubercles of certain cala- 

 mitean casts. 



In photograph 6 (PI. 27, fig. G), a copy, the original of which has been already indi- 

 cated (Williamson and Scott, Phil, trans, roy. soc, 1894, B., pi. 78, fig. 11), is a representa- 

 tion of the nodal arrangement of the vascular strands of a Calami te, as seen in tangential 

 section. It will be observed that these have, generally speaking, the same relation to 

 each other at the node as is exemplified in our photograph 3 (PI. 29, fig. 3) of E. hiemale. 

 In the lower ends of the upper medullary rays are situated certain structures which 

 Williamson and Scott yop. cit., p. 876) consider to be leaf-traces. In photographs 4 and 

 5 (PI. 27, figs. 4, 5) , which are taken from Williamson's earlier memoirs (Phil, trans, 

 roy. soc, 1871, pi. 26, fig. 22; ibid, 1878, pi. 20, fig. 23), these are represented as being 

 the vascular strands of branches. The changed interpretation of the later memoir need 

 not be considered for the present, although, as will be indicated subsequently, it is of some 

 importance. In the later memoir already referred to, Williamson and Scott (Phil, trans, 

 roy. soc, 1894, B., pi. 78, fig. 11) make the statement that the leaf-traces in the Calamites 

 originated from the protoxylem of the bundles of the lower internode, and consequently, 

 it may be assumed, below the nodal wood, since they inform us that the protoxylem came 

 to an end below the node in Calamites, just as it does in the Equisetaceae. Returning 

 now to the statement that the leaf-traces are found in the upper medullary rays and con- 

 sequently above the nodal wood, it may be asked how they have got into this supranodal 



