154 ANCIENT PLANTS 



some may be wedge-shaped like those in fig. 112, and 

 others almost hairlike. This naturally suggests com- 

 parison with water plants, which have finely divided 

 submerged leaves and expanded aerial ones. In the 

 case of Sphenophylhtm, however, the divided leaves 

 sometimes come at the upper ends of the stems, quite 

 near the cones, and so can hardly have been those of 

 a submerged part. The very delicate stems and some 

 points in their internal anatomy suggest that the plant 



Fig. 112. — Impression of Sphenophyllum Leaves attached to the Stem, showing the 

 wedge-shaped leaflets arranged in whorls 



was a trailing creeper which supported itself on the 

 stouter stems of other plants. 



The stems were ribbed, but unlike those of the Cala- 

 mites the ribs ran straight down the stem through the 

 nodes, and did not alternate there, so that the bundles 

 at the node did not branch and fuse as they did in 

 Calamites. 



The external appearance of the long slender cones 

 was not unlike that of the Calamite cones, though their 

 internal details .showed important distinctions. 



In one noticeable external feature the plants differed 

 from those of the last two groups considered, and that 

 was in their size. Palaeozoic Lycopods and Equisetacese 

 reached the dimensions of great trees, but hitherto no 



