CHAPTER II 



EQUISETALES VEGETATIVE STRUCTURE 



Calamites ; Arthrodendron ; Calamodendron ; 

 Protocalamites 



I. The Calamarieae. — We know that among living 

 Pteridophyta we can distinguish three great classes or 

 phyla : the Ferns, the Lycopods, and the Horsetails. 

 The last-mentioned group, though manifestly quite as 

 distinct a stock as the other two, is now represented 

 only by the single genus Equisetum, the species of 

 which exhibit but small variety of structure. We 

 might naturally suppose that in Equisetum, a group 

 at once so isolated and so limited, we have the last 

 surviving remnant of a once more extensive family. 

 Fossil botany affords the most remarkable proofs of 

 the truth of this hypothesis, and indeed shows that in 

 the Carboniferous period the Horsetail stock was 

 among the best-represented divisions of the Vegetable 

 Kingdom. In fact, we may safely say that any adequate 

 knowledge of the Equisetales must be derived to a 

 much greater extent from the study of the extinct 

 forms than from that of the few surviving repre- 

 sentatives. In saying this, I am assuming that all 

 the Palaeozoic plants known as Calamarieae were of 



is 



