ISO SPORANGIOPHORES AND SPOROPHYLLS 



bracts or leaf-teeth : thus, in the modern Equisetum and in the ancient 

 Bornia they occupy the whole strobilus in large numbers, and bracts are 

 absent ; in Phyllotheca the fertile spikes are interrupted by occasional whorls 

 of vegetative leaves : in Calamostachys the strobilus bears successive whorls 

 of bracts, and whorls of sporangiophores alternate with them ; but even here 

 they do not show exact numerical correspondence with the bracts, which, 

 moreover, alternate independently of them. Further, their longitudinal 



br 



br 



ax 



FIG. 81. 



Palacostachya. Diagram of cone in 

 radial section. a.r = axis, which bears 

 verticils of bracts (br) with peltate 

 sporangiophores (sf) in their axils. 

 si = sporangia. (After Renault.) From 

 Scott. 



Archncocalainites. Part of 

 cone showing the axis (.r) 

 in surface view, bearing 

 superposed verticils of peltate 

 sporangiophores (.<:/>) without 

 bracts. sm = sporangia. (After 

 Renault.) From Soitt. 



FIG. 83. 



H elminthostachys .;cylnnifa. 

 Young spike in oblique profile : 

 the primordia of .sporangio- 

 phores are densely clustered "n 

 the margin. Magnified. (After 

 Goebel.) 



position relatively to the bracts varies, for in Calamostachys they are placed 

 midway between the whorl of bracts, in Palaeostachya in their axils, in 

 Cingularia immediately below them. This indefmiteness of relation of 

 the spore-bearing bodies to the bract-leaves in number and position, as 

 seen among the Equisetales, when taken together with the difference of 

 function, points to their being a separate category of members from them 

 (Figs. 80, 81, 82). 1 



1 This statement is not in accord with the opinions expressed by Prof. Lignier, whicli 

 will be considered where the Equisetales are specially treated in Part II. 



