168 HISTORICAL PALAEONTOLOGY. 



uncompressed stems growing in an erect position, and some- 

 times attaining a length of twenty feet or more. Externally, the 

 stems are longitudinally ribbed, with transverse joints at regular 

 intervals, these joints giving origin to a whorl of branchlets, 

 which may or may not give origin to similar whorls of smaller 

 branchlets still. The stems, further, were hollow, with trans- 

 verse partitions at the joints, and having neither true wood nor 

 bark, but only a thin external fibrous shell. There can be little 

 doubt but that the Calamites are properly regarded as colossal 

 representatives of the little Horse-tails (Equisetacece) of the 

 present day. They agree with these not only in the general 

 details of their organization, but also in the fact that the fruit 

 was a species of cone, bearing " spore-cases " under scales. 

 According to Principal Dawson, the Calamites " grew in dense 



Fig. 108.0dontopteris SchlotheimU. Carboniferous, Europe and North America. 



brakes on the sandy 'and muddy flats, subject to inundation, 

 or perhaps even in water; and they had the power of budding 

 out from the base of the stem, so as to form clumps of plants, 

 and also of securing their foothold by numerous cord-like roots 

 proceeding from various heights on the lower part of the 

 stem. " 



The Lepidodendroids, represented mainly by the genus 

 Lepidodendron itself (fig. no), were large tree-like plants, 

 which attain their maximum in the Carboniferous period, but 



