374 



EOUISETALES 



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

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



FIG. 198. 



ni-iti'ii (iodvancnsis. Two-thirds the natural .si/t. (After O. Feistmantel, from 

 Engler and Prantl, Nat. PJlauzenfain.) 



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

 construction : the nearest to the guisetum-type is the ancient Archaco- 



calamites (Jlorniii), 1 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. 



The latter was the more prevalent type 

 among the early Equisetales : in them the sterile 

 leaf-whorls and the whorls of sporangiophores 

 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, Rassin Hmiillcr et Pennien if A lit tin it if Epinac, vol. ii., p. So, Plate 42. 



Kir,. 199. 



A sterocalamites scrobicnlatus. 

 Schlotheim (./) from the culm. 

 Fragment of a leafy shoot, re- 

 duced in lull iis natural si/e. 

 (After Stur, from Zeiller, Palco- 

 botanique.) 



