354 



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. 



C. 

 D. 



Fig. 95. Calamostachys Binneyana (Carr.). 

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

 Tangential section showing portions of two sterile discs, 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 free 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 Uquisetum 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 



