364 



CALAMITES. 



[CH. 



single layer of cells (fig. 95, B) which present a characteristic 

 appearance in surface-view (fig. 95, C), the thin walls being 



A. 

 B. 



G. 

 D. 



Fig. 95. Calamostachys Binneyana (Carr.). 

 A aporangiophore and one sporangium, t, vascular bundle, x 45. 

 Tangential section showing portions of two sterile discs, 6, 6 ; a sporan- 

 giophore, a, with its four sporangia, in two of which are seen the spores ; 

 t, vascular bundle, x 35. 



Surface-view of cells of a sporangium wall, x 130. 

 Spores and remains of mother-cells, x 130. 

 (After "Williamson and Scott.) 



crossed at right angles by small vertical plates. In the 

 tangential section of the coherent sterile whorls (fig. 95, B, 

 b and b) the vascular strands are occasionally seen in 

 transverse section (fig. 95, B, t), as they pass outwards to the 

 several fi-ee bracts. 



The spores in Calamostachys Binneyana are all of the same 

 size, and no macrospores have ever been seen. In well pre- 

 served specimens tetrads of spores may be seen, still enclosed by 

 the wall of the spore-mother-cell (fig. 95, A and D); and the torn 

 remnants of the mother-cell sometimes simulate in appearance 

 the elaters of an Equisetum spore. In surface-view a spore 

 often shows clearly the three-rayed marking, which is a charac- 

 teristic feature of daughter-cells formed in a tetrad from a 



