374 



EQUISETALES 



The Calamarian strobili were terminal on the axes, but they had a more 

 elongated form than is usual in Equisetum (Fig. 200) : sometimes they 



FIG. 198. 



Schizoneura Godwanensis. Two-thirds the natural size. (After O. Feistmantel, from 

 Engler and Prantl, Nat. Pflanzenfain.} 



extended to a length of 30 cm. (Potonie). They differed also in their 

 construction : the nearest to the Equisetum-typQ is the ancient Archaeo- 



calamites (Bornia)?- characteristic of the oldest 

 Carboniferous strata, and of the upper Devonian 

 (Fig. 201). Its strobilus is essentially like that 

 of Equisetum, having no sterile bracts intervening 

 between the whorls of eight to ten sporangio- 

 phores. These whorls did not alternate, but 

 neither did the whorls of branched leaves in this 

 early type. Here it would appear that there is a 

 more complete differentiation of the reproductive 

 from the vegetative region than is the case where, 

 as in other Calamarians, sterile bracts are dis- 

 tributed throughout the strobilus. 

 Asterocaiamites scrobicuiatus. ^ } atter was t he more prevalent type 



bchlotneim (sf) from the culm. 



Fragment of a leafy shoot, re- amO ng the early Equisetales : in them the sterile 



duced to hall its natural size. 



(After Stur, from Zeiiier, Paieo- leaf-whorls and the whorls of sporangiophores 



botanique.) 



regularly succeeded one another, as it is seen 



in Calamostachys, and is well shown in C. Binneyana, which is the 

 best known type (Fig. 202). The sterile whorls are commonly composed 



1 Renault, Bassin Hoitiller et Per mien d? Autir.i et tfEpinac, vol. ii., p. 80, Plate 42. 



FIG. 





