Manchester Meinoirs, Vol. hi. (191 2), No. IT. 9 



the branch node. If this were quite conclusively proved, 

 it would be sufficient to settle the question. But apart 

 from this possibly doubtful evidence, there is something 

 to guide us in the shape of the scars themselves. The 

 Manchester Museum collection includes several fine pre- 

 parations showing the microscopic structure of branches 

 cut in transverse section near their points of emergence. 

 Others are figured by Williamson and Scott. Exami- 

 nation of a series of longitudinal stem sections shows that 

 at certain depths near the surface, the wood of the branch 

 is developed unequally round the pith, the greater amount 

 occurring on the upper side of the branch. The branch 

 scars in the fossil are true to this type ; the deepest part — 

 that which is presumably the pith centre — is markedly 

 eccentric, and lies nearer the nodal line to which the 

 branch belongs. Again, in several of the Calauiites 

 figured by Stur {see below), the scar-bearing branches are 

 still attached to their parent stems, and there can be no 

 possible dispute about which is the basal region — in all of 

 them the short internodes lie above the branch node, as I 

 place them in the Bradford specimen. Accepting these 

 three points as dependable evidence — the position of the 

 line of leaf-scars below the branch scars, the eccentricity 

 of the umbilicus, and the similarity to other branching 

 stems of undoubtedly correct interpretation — I conclude 

 that A {Plate) is the upper level of this stem. 



Interpretation of Variation in Length 

 OF Internodes. 



That the internodes in Calamitean stems may vary 

 in length in any one specimen, and that there may be a 

 periodicity in that variation has been noted and figured 

 by several writers. Except in the last of the instances 



