Manchester Memoirs, 'Vol. liv. (1910), No. IT 13 



C. OldhaDiia) — the small number of appendages and of 

 primary vascular strands, and the solid medulla. I think 

 it will be generally admitted that in these respects, these 

 cones are more primitive than the rest, and I would 

 regard CalauiostacJiys Biiineyana as the most primitiv^e 

 calamitean cone yet known. One can scarcely believe 

 that the striking similarities of this cone, as here 

 interpreted, with the cones of SphenopJiylhim are purely 

 accidental. The stele is still characteristically triarch, 

 and the vascular strands non-alternating. As regards the 

 stele, I would suggest that in the Sphenophylls and 

 Calamites we have a course of evolution parallel with 

 that which Dr. Scott (Scott :o2) has so well described in 

 another group ; that in SpheiiopJiyllinn we have the 

 primitive type with entirely centripetal primary xylem, 

 that in CalainostacJiys Binneyana we have the centripetal 

 tissue reduced to a somewhat peculiar medulla and 

 centrifugal xylem replacing the old wood functionally, 

 while in the more advanced types of CalainostacJiys we 

 have the medulla still further degenerating, and the old 

 triarch condition graduall)' lost as the result of multi- 

 plication of the appendages in the manner suggested by 

 Lignier (Lignier :03). In all the cones of Calamites 

 the primitive direct course of the bundles appears to have 

 been maintained, that only vanishing in the less con- 

 servative veGfetative shoots. 



