148 



ANCIENT PLANTS 



Yet in their external appearance they probably resembled 

 the living genus in all essentials, and the groves of the 

 larger ones of to-day growing in the marshes probably 

 have the appearance that the palaeozoic plants would 

 have had if looked at through a reversed opera glass. 

 Fig. 104 is a photograph of some of the small 

 branches of a Calamite, in which the ribbed stem can 



be seen, and on the 

 small side twigs the 

 fine, pointed leaves 

 lying in whorls. 



In most of the 

 fossil specimens, how- 

 ever, particularly the 

 larger ones, the ribs 

 are not those of the 

 true surface, but are 

 those marked on the 

 internal cast of the 

 pith. 



Among tissue 

 petrifactions there 

 are many Calamite 

 stems of various 

 stages of growth. In 

 the very young ones 

 there are only pri- 

 mary bundles, and 

 these little stems are like those of a living Equisetum in 

 their anatomy, and have a hollow pith and small vascular 

 bundles with canals associated. The fossil forms, how- 

 ever, soon began to grow secondary wood, which devel- 

 oped in regular radial rows from a cambium behind the 

 primary bundles and joined to a complete ring. 



A stem in this stage of development is seen in fig. 105, 

 where only the wood and internal tissues are preserved. 

 The very characteristic canals associated with the primary 

 bundles are clearly shown. The amount of secondary 



CO! 



Fig. 105. — Transverse Section of Calamites Stem 

 with Secondary Wood w formed in Regular Radial 

 Rows in a Solid Ring 



c, Canals associated with the primary bundles ; /, 

 cells of the pith, which is hollow with a cavity /. 

 cor, Cortex and outer tissues well preserved. (Micro- 

 photo. ) 



