RESEARCHES ON THE CARBONIFEROUS FLORA. 257 



Dicotyledons " on account of their anatomical similarity to 

 that class, while the latter were left among Cryptogams. 



Williamson, in the passage above cited, shows that 

 though already beginning to disbelieve in Brongniart's two 

 groups, he still attached great systematic importance to the 

 presence of secondary tissues. 



In the next year our author published a paper "On a 

 New Form of Calamitean Strobilus " (23). This relates to 

 an interesting cone, more fully described at a much later date 

 (14), of the type subsequently placed by Weiss in his 

 genus Pal&ostackya (37) (vol. ii., p. 161), in which the pel- 

 tate scales arise in or near the axils of the bracts, instead of 

 being inserted midway between their whorls as in Calamo- 

 stachys. Williamson now (1870) arrived at the conclusion 

 that "the Calamites constitute essentially one large group of 

 plants". " Their stems were exogenous so far as the woody 

 cylinder was concerned, and closely related to those of the 

 Dadoxylons. But on the other hand their fructification was 

 Cryptogamic." He inferred that the Calamites were " a 

 generalised type, afterwards differentiated through the 

 Dadoxylons and the oolitic Equiseta, into the modern 

 types of Conifera^ and Equisetiform plants ". The mere 

 occurrence of secondary growth was no doubt an insufficient 

 basis for such a conclusion, though, in the opinion of the 

 present writer, the possibility of a relationship between 

 Calamarieae and primitive Coniferous Gymnosperms may 

 again have to be considered. 



It will be of interest to trace rapidly the further develop- 

 ment of Williamson's work on the Calamites. The first 

 memoir of the great series in the Philosophical Transactions 

 of the Royal Society is entirely devoted to this group. The 

 author states that " the fundamental aim of this memoir is 

 to demonstrate the unity of type existing among the British 

 Calamites". In other words he showed that all British 

 Calamites, of which the structure can be ascertained, are 

 alike in possessing secondary tissues, and consequently that 

 Brongniart's distinction between Crvptogamic Calamites and 

 Phanerogamic Calamodendra has no existence so far as our 

 native Carboniferous Flora is concerned. In the light of 



