1492 



THALLOPHYTES. 



which correspond with the lateral processes, and open by pores upon 

 the surface. On the other hand, where there are two orders of 

 lateral offshoots (as in Cymofiolia), a double calcareous cylinder is 

 produced, the inner one corresponding with the axis and the primary 

 whorled processes, while the outer one is formed by the confluent 

 clavate ends of the secondary processes. The spherical sporangia 

 may also become calcined, and may present themselves as rounded 



Fig. 1360. — Cymopolia barbata (=C. rosarium), from the Canary Islands (Recent), a, A 

 specimen of the natural size, showing the divided thallus ; b, Transverse section through a seg- 

 ment of the stem, showing a whorl of lateral processes, of which some are sterile and some 

 fertile ; c, Part of the same whorl enlarged still further, showing the primary lateral processes (c), 

 giving off sterile offshoots (b), and spherical sporangia (a). (After Schimper and Zittel.) 



cavities in the skeleton. Finally, the cylindrical skeleton may be 

 composed of annular segments or may be undivided, according as 

 the axial cell is, or is not, constricted at intervals. In the former 

 case, the segments are often readily capable of separation, and in 

 fossil examples often present themselves as detached calcareous 

 rings. 



When the calcareous skeleton is all that is open to our inspection, 

 as in fossil specimens, the transverse canals with their superficial 



