SPHENOPSIDA 105 



bearing them may have been pendulous. It is probable, 

 therefore, that the cones were pendulous, too. 



The cones of Calamites were borne in a variety of ways, 

 in some species singly at the nodes, in others in terminal 

 groups or infructescences or on specialized branches. ^ Many 

 species are known, but most of them are placed in one or 

 other of the two genera Calamostachys and Palaeostachya. 

 As originally defined, these two genera were clearly distinct, 

 but, in the light of many newly discovered species, Andrews^ 

 has questioned whether the distinction is now justified. In 

 both genera there were whorls of peltate sporangiophores 

 bearing four reflexed sporangia (Figs. 1 61 and 1 6 J), alternating 

 with whorls of bracts fused into a disc near their point of 

 attachment. Whereas the sporangiophores were in vertical 

 rows, the bracts in successive whorls alternated with one 

 another. While the number of bracts in a whorl bore a 

 definite relationship to the number of sporangiophores, the 

 actual numbers varied from species to species and, some- 

 times, from individual to individual. Calamostachys Binne- 

 yana, a cone about 3-5 cm long and 7-5 mm wide, had six 

 sporangiophores in each whorl and twelve bracts. C. 

 magnae-crucis was more complicated, in having alternating 

 vascular bundles in successive internodes within the cone 

 and in having sporangiophores and bracts so numbered that, 

 if 'n' were the number of vascular bundles, then the number 

 of sporangiophores was in in each whorl and the number of 

 bracts 3n; the number 'n' could be either seven or eight. 

 Most species were homosporous, but some were definitely 

 heterosporous. Thus, in C. casheana the megaspores were 

 three or four times the size of the microspores, while in 

 C americana they were about twice the size. 



Whereas the sporangiophores of Calamostachys stood out 

 at right angles to the cone axis, those oi Palaeostachya stood 

 out at an angle of about 45°, and in some species they appear 

 to have been in the axil of the bract whorl below. P. vera had 

 eight to ten sporangiophores in each whorl and twice as 



