RELATIONS OF CALAMODENDRON TO CALAMITES. 259 



such as had been found in Brongniart's Calamodendron, 

 but he saw that the radiating masses of cellular tissue 

 (the primary medullary rays of my memoir) which alter- 

 nated with the vascular wedges, differed from those of 

 Cottars plant ; therefore he left the latter in Brongniart's 

 genus Calamodendron, whilst for the reception of the 

 others he instituted the new genus Arthropitus ^. Brong- 

 niart's genus Calamodendron, as defined on p. 256, un- 

 doubtedly comprehended Goppert's new genus ; the French 

 author had been misled by his ignorance of the fact that 

 both these genera possessed an exogenous vascular zone, 

 which zone he obviously regarded as the chief feature 

 distinguishing his Calamodendron from Calamites. M. 

 Grand'Eury has followed Goppert in accepting his genus 

 Arthropitus ; but consistently with the Brongniartian views 

 which he adopted when he published his ' Flore Carbonif ere 

 du Departement de la Loire/ he there placed the genus 

 along with Calamodendron in his " Famille des Calamoden- 

 drees," regarding both as Gymnospermous genera. 



From 1869, the time of the publication of my Cala- 

 mitean memoir already referred to, I have continued 

 to demonstrate that all the Carboniferous Calamites 

 began to develop exogenously a vascular zone even in 

 their youngest state, and that the supposed non-exogenous 

 Equisetiform type existed only in the minds of a few 

 men, unbelievers in exogenous Cryptogams. Unger's 

 Arthropitus is, I have long been convinced, merely an 

 ordinary Calamite, in which the development of the 

 exogenous zone has made some conspicuous progress. 

 M. Grand'Eury himself has advanced so far as to recognize 

 this fact. In his ' Determination Specifique des Empreints 

 vegetales du terrain houiller^' ■\, he says : — " J'ai assez bien 



* 'Die fossile Flora der Permischen Formation/ p. 179. 

 t ' Comptes Rendus,' Seance du 22 fevrier, 1886. 



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