FERNS— FRUCTIFICATIONS 



2 93 



lamina being well developed, like that of a vegetative 

 frond rather than a specialised sporophyll. The 

 pinnules are much incurved, and the sporangia are 

 seated on their margins. In the section figured, several 



Fig. 112. — Pieridotheca. Williamsonii. Group of annulate sporangia, seen in section, 

 parallel to surface of frond. The sporangia contain numerous spores ; at «, the 

 annulus is specially clear. /, /, r, parts of tissue of the fertile pinnules. X 36. S. 

 Coll. 215 (Coal-measures). (G. T. G.) 



pinnules, cut in various planes, are shown. The 

 sporangia are sessile, with a multicellular base, and are 

 of nearly spherical form, except where their sides are 

 flattened by mutual pressure. The most striking 

 feature of the sporangia, which contain numerous small 



