PALEOBOTANY BERRY. 



313 



the center there was a triangular strand of primary wood without 

 any pith or parenchyma and either triaivh or hexarch in structure, 

 with the protoxylem or primitive spiral elements at the angles and 

 centripedal in its development. The spiral elements sometimes 

 pass into reticulate tracheids and the later and more central tra- 



Fig. 6.— Types of fructifications of the Sphenophyllales. 



• 



1. Sphenophylluni trichomatosum (after Stur). 



2. Bowmannites roemeri (after Solms). 



3. Sphenophyllostachys (after Zeiller). 



4a. Sphenophyllum majus from above (after Kidston). 



4b. Two nodes of preceding from the side (after Kidston). 



5. Sphenophyllum dawsoni showing two whorls in median longitudinal section and external view of a 

 whorl of bracts (after Scott). 



6a. Diagram of transverse section of a complete sporophyll of Cheirostrobus (after Scot I ). 



6b. Diagram of median longitudinal section (after Scott). 



7a. Sphenophyllum fertile, median longitudinal section at a node (after Scott): vl, ventral lobe of sporo- 

 phyll; vsl, vs2, segments into which it splits; dl, dorsal lobe of sporophyll; dsl, ds2, segments into 

 which it splits. 



7b. Diagram of a single sporophyll as it would appear in a transverse section of the cone (after Scott): 

 vl, vllj ventral lobes; dl, dll, dorsal lobes. 



cheids are pitted. Secondary wood formation commenced early in 

 the ontogeny by the activity of a normal cambium. The secondary 

 wood had its elements very regularly arranged and consisted of 

 radial series of large tracheids with bordered pits, chiefly on their 

 radial walls. Interspersed among the tracheids were vertical 

 strands of parenchyma connected radially by short cells or strands 



