178 PROF. W. C. WILLIAMSON ON THE STRUCTURE 



pressions marked the external line of the cellular ones — 

 an arrangement reversing that which these structures bear 

 to the surface of the pith. 



But Mr. Butterworth^s collection has, in addition, fur- 

 nished me with the cone of my plant. It has been of 

 much larger dimensions than those described by Mr. 

 Binney, as well as much more complex in its internal 

 structure, and otherwise distinct ; but that it belonged to 

 my plant is shown by the reticulated vessels of its central 

 axis, as well as by their curious arched arrangement when 

 crossing the nodes — an arrangement to which I have 

 already referred as constituting so remarkable a feature of 

 the plant which I have described. From this axis there 

 are given off at each node ten well-defined radiating pe- 

 duncles, each of which divides into bract-like appendages, 

 which bend first downwards, and then curve upwards and 

 outwards, first sending upwards into the cone two sporan- 

 gium-bearers. The sporangia have walls consisting of a 

 single layer of oblong tabular cells ; and their interior is 

 filled with defined cellular tissue. Each spore seems to 

 be a spherical body, consisting of two layers, exhibiting 

 no trace of elaters or external appendages. I have but 

 briefly indicated a few of the features of this beautiful 

 cone, because its more minute and elaborate features de- 

 mand that I should devote to it a separate memoir, 

 which I hope to be able to lay before the Society at an 

 early date. The peculiarities of this cone seem to justify 

 the establishment of the genus Calamopitus. 



All the additional facts which Mr. Butterworth's in- 

 valuable specimens have revealed confirm my pre^dous 

 conviction of the close affinity existing between the struc- 

 ture and growth of the woody wedges of my Calamite and 

 corresponding wedges taken from the stems of some Da- 

 doxylons. Of course this resemblance implies that in 

 their growth these wedges have been exogenous, which is 



