HORSETAILS 203 



Roots were borne in abundance on the lower 

 part of the stem; in a specimen described by 

 Grand' Eury the stem bore roots up to a height 

 of nine feet from its base. 



We will now describe the main outlines of 

 Calamitean structure, for all the organs have 

 been found beautifully preserved; the best speci- 

 mens come partly from the coal-balls of the 

 English Lower Coal Measures, partly from the 

 Upper Coal Measures of France. Just as in 

 Equisetum, the pith was hollow in the main stem, 

 and in all except the finest branches. The com- 

 monest Calamite fossils are casts of the hollow 

 pith. Some of these casts are over a foot in 

 diameter, which gives some idea of the size of the 

 tree which had such a pith. 



In the young condition, the stem or branch of 

 a Calamite had practically the same structure as 

 an Equisetum; there was a ring of separate vas- 

 cular strands, and every strand had a canal on its 

 inner side. Any botanist looking at a section of 

 such a young Calamite stem would at once call 

 it "a fossil Equisetum" But the Calamite did 

 not stop at the Equisetum stage. It immediately 

 began to thicken its stem, exactly like a Gym- 

 nospermous or Dicotyledonous tree. A broad 

 zone of secondary wood was added, traversed by 

 medullary rays, with a layer of bast to the outside 

 and the cambium between the two; the delicate 



