384 ARCHAEOCALAMITES. [CH. 



The structure of the wood agrees with that of some forms of 

 Arthropitys. The strobili consist of an articulated axis bearing 

 whorls of sporangiophores, and each sporangiophore has four 

 sporangia. Our knowledge of the fertile shoots is, however, 

 very imperfect. 



Eenault^ has recently described the structure of the wood 

 in some small silicified stems of Archaeocalamites from Autun. 

 A large hollow pith is surrounded by a cylinder of wood 

 consisting of wedge-shaped groups of xylem tracheids associated 

 with secondary medullary rays ; at the apex of each primary 

 xylem group there is a carinal canal. The primary medullary 

 rays appear to have been bridged across by bands of xylem at 

 an early stage of secondary thickening, as in the Calamite 

 of fig. 83, D. 



Our knowledge of the cones of Archaeocalarnites is far from 

 satisfactory. Renault^ has recently described a small fertile 

 branch bearing a succession of verticils of sporangiophores; 

 each sporangiophore stands at right angles to the axis of 

 the cone and be^-rs four sporangia, as in Calamostachys. It is 

 not clear how far there is better evidence than that afforded by 

 the association of the specimen with pith-casts of stems, for 

 referring this cone to Archaeocalamites, but the association of 

 vegetative and fertile shoots certainly suggests an organic 

 connection. The cone described by the French author agrees 

 with Equisetiim in the absence of sterile bracts between the 

 whorls of sporangiophores. It is an interesting fact that such 

 a distinctly Equisetaceous strobilus is known to have existed 

 in Lower Carboniferous rocks. 



Stur^ has also described Archaeocalamites at considerable 

 length ; he gives several good figures of stem-casts and foliage- 

 shoots bearing long and often forked narrow leaves. The same 

 writer describes specimens of imperfectly preserved cones in 

 which portions of whorls of forked filiform leaves are given off 



1 Kenault (96), p. 80; (93), Pis. xlii. and xliii. Since the above was written 

 an account of the internal structure of Archaeocalamites has been published by 

 Solms-Laubach (97) ; he describes the wood as being of the Arthropitys type. 



2 Eenault, loc. cit. PI. xlii. figs. 6 and 7. 

 » Stur (75), p. 2, Pis. ii.— v. 



