THE PTERIDOPIIVrA 



341 



contains. Across the stem at each node extends a sohd parti- 

 tion or diaphragm. The stems may be branched or unbranched. 

 As in the lycopods, the sporangia are borne in terminal cones 

 (Fig. 214). The sporophylls, however, are not at all leaf -like but 



Fig. 215. — Transverse section (diagrammatic) of the stem of Equisetum. 

 Note the large central cavity, the air chambers opposite the stem furrows, and 

 the smaller ones in the bundles. The fibro-vascular system is much reduced, 

 consisting of a ring of small bundles, each with two minute arms of wood and a 

 patch of bast between. Wood black, bast dotted. 



Fig. 216. — Gametophytes of Equisetum. A, male gametophyto, showing 

 antheridia. B, sperms. C, female gametophyte, showing the long, branching 

 lobes with archegonia at their bases. (A and C after Ilofmcister, B after Schachl) . 



are somewhat shield-shaped and project outward at right angles 

 to the cone axis. On their under or inner surfaces are borne 

 a row of sporangia. The spores are all alike externally, but a 



