ii6 Dr. W. C. Williamson on 



absolute continuity with the more external Cortex. In 

 longitudinal sections this zone pursues a somewhat 

 undulating course, touching the periphery of the Tracheal 

 cylinder at points where leaf-traces are originating (C.N. 

 419c), and at others uniting with the inner edge of the 

 outer Cortex (C.N. 4i9e). 



Sometimes the latter is an uniform parenchyma com- 

 posed of rather thin-walled cells (C.N. 627), but in one 

 longtitudinal section (C.N. 4i9e) this undulating inner zone 

 is almost continuously united to the outer one by a mass 

 of loosely aggregated cells, the entire structure being con- 

 spicuous for the coarseness of its tissues and the thickness 

 of the cell-walls. 



In transverse sections of the vegetative twigs, the 

 periphery of the cortex has an undulating outline, with here 

 and there small projecting points, that may possibly have 

 been the bases of leaves. In such sections a characteristic 

 feature of the plant is seen in this outer cortex, viz. : a circle 

 of large dark-coloured areas alternating with lighter bands 

 that separate them (See Memoir XVI., Fig 19, i", i"). This 

 feature scarcely reappears in the sections of the Strobili ; 

 Slightly so in C.N. 627. 



I have long had a conviction that the remarkable 

 Strobilus represented on Figs. 38 to 57, Plate 22 of my 

 Memoir I., belonged to L. Spenceri, and the fortunate 

 discovery by my friend Mr. Lomax of the specimen 

 C.N. 642e, figured in Memoir B.B., Figs. 41 and 42, proves 

 the correctness of my hypothesis. 



The characteristics of the Strobilus are even more 

 strongly individualised than are the vegetative twigs. As 

 already shewn, the axial structures are virtually identical in 

 the twigs and the fruits, with the single difference that the 

 leaf-traces of the former supply the sporangiophores of the 

 latter. Each sporangiophore (loc. cit. fig. 24) supports a 

 single more or less spherical sporangium. The contents of 



