36 PROF. W. C. WILLIAMSON ON THE 



I 



with the Calamites and that which I have now described, 

 the case is altogether different. In both these the vas- 

 cular tissues of the axis occupy the exact centre of the stem, 

 or what would have been the centre of the nstulo-medul- 

 lary cavity of a Calamite, whilst all their cellular layers are 

 external to the vessels. Now, whilst this is an arrangment 

 common enough amongst some Ferns, and still more 

 so amongst the Lycopodiacese, nothing approaching it 

 has been seen, either amongst the fossil Calamites or 

 amongst the recent Equisetaceae, with which some of our 

 phytologists are so anxious to identify the Calamites. 

 Mr. Carruthers very correctly acknowledges that "the 

 axis of the strobilus has a bundle of fine scalariform tissue 

 in its centre, forming about a third of its diameter, and 

 generally appearing free from the surrounding cellular 

 tissue, which is composed of somewhat elongated cells." 

 (" On the Structure of the Fruit of Calamites," by Wm. 

 Carruthers, Esq., F.L.S., Journal of Botany, Dec. 1867.) 



Now I cannot conceive the possibility of so complete a 

 reversal taking place in the relative positions of the cel- 

 lular and vascular tissues of the axis as must have occurred 

 if these fruits ever grew upon a Calamitean stem. 



In the case of the plant which I have just described, 

 there is no room for doubting that its foliage was arranged 

 in verticils. Mr. Binney's specimens, especially that re- 

 presented in his pi. vi. fig. 4, are unmistakably associated 

 with the leaves of Asterophyllites ; and identical specimens 

 in my own cabinet, apparently belonging to the same type 

 as Mr. Binney's, are similarly associated. It must be re- 

 membered also that both Sternberg and Schimper have 

 figured very similar fruits, attached to specimens of the 

 closely allied genus Sphenophyllum. Hence it is clear 

 that, if my plant is of the same type as some of those just 

 referred to (and that such is the case there can be no 

 question) , we have but a limited range within which to 



