90 BOTANICAL GAZETTE [august 



Will the comparison of stem anatomy throw any favorable 

 light upon the question of a possible remote phyletic connection 

 between the Calamites and the Lycopods? A comparison of the 

 stem structure of such lycopodian forms as Sigillaria Menardi 

 (Brongniart 9) (fig. 13) with a calamitean form such as Calamites 

 (Asteromyelon) Augustodunense (Renault 23) (fig. 14), an appendage 

 of the stem, probably a root, of some species of Calamites, will at 

 once reveal a similarity which extends to details. In both the xylem 

 consists of a ring of somewhat wedge-shaped elements, distinct from 

 one another but nearly or quite in contact in their wider portions 

 except for narrow interposing medullary rays. Each xylem 

 "wedge" consists of both primary and secondary xylem, the 

 relatively small bundle of centripetal protoxylem occupying the 

 apex. In each case the outer side of the protoxylem bundle is 

 occupied by small spiral tracheids, while the remainder of the 

 bundle, the convex inner portion, consists of larger scalariform 

 tracheids. These primary strands are distinctly separated from 

 one another. The secondary xylem consists of large radially 

 arranged scalariform tracheids. Beyond the xylem is a narrow 

 zone of phloem, and beyond this the cortex. Agreement such as 

 this in the stem anatomy of forms from different phyla is very 

 impressive.^ On the other hand, we can think of no lycopodian 

 stem which even remotely suggests the characteristic triarch or 

 hexarch protostele of the Sphenophyllales. The evidence from 

 anatomy then gives a certain plausibility to the suggestion that 

 Calamostachys Grand'Euryi Ren. and C. Decaisnei Ren. may 

 represent a calamitean ancestor of Cantheliophonis. "True 

 phylogenetic homologies may fairly be expected to be traced 

 between plants which appear to belong to* the same natural series" 

 (Bower 5), and accordingly the brace in the sporangiophore of 

 Cantheliophorus and the radially symmetrical sporangiophore in 

 Palaeostachya and Calamostachys may come to be considered 



3 If by chance anyone should contend, though it is rather beside the point, that 

 the force of this comparison is weakened somewhat by the fact that centripetal xylem, 

 as VAN TiEGHEM first pointed out, is common to the roots of all vascular plants, we 

 should say that the force of this comparison is correspondingly reinforced by the fact 

 that this type of protoxylem characterizes the stem of Prolocalamitcs pettycurensis 

 (Scott) Lotsy (Scott 28) from the Lower Carboniferous of Scotland. 



