160 



D. H. Scott. 



stroiîgl}' resemble those of CaJamosfachys, and are equal in number 

 to the bundles of the axis (norraall}' 18) and opposite to them. The 

 number of bracts is probably the same, certainly not dmible as in Cala- 

 mostacliys:' '"The vascular strands supplj'ing bracts and sporangio- 

 phores arise from the same node. The bract-bundles pass almost 

 horizontally through the cortex to the bracts they supplj'. The spo- 

 rangiophore-bundles ascend through half an internode in contact with 

 their corresponding axial Imndles, then sharpl}' double back and 

 descend .... to enter the sporangioi)hores." 



'•Hence, from the evidence of vascular 

 supply the sporangiophores may be regarded as 

 virtually axillary, but their present axillary posi- 

 tion is secondary, not primarj^" 



It thus appears probable that Palaeostachya, 

 instead of representing, as has been supposed, 

 a link between the Sphenophyllales and the Cala- 

 mostachys form of strobilus, may rather be regar- 

 ded as a moditication of the Calamostachys type. 

 None the less, the evidence of Calamostachys 

 itself is sufficient to establish a clear relation 

 between the ( 'alamarian fructifications and those 

 of the Sphenophyllales. 



The modification of the strobilus had, how- 

 ever, gone further, even in early Palaeozoic 

 times. Kenault (1896) has described certain 

 fragmentary fructifications, of Lower Carboni- 

 ferous age, which he attributes on good grounds 

 to Archaeocalamitcs (Fig. 7). The axis bears 

 superposed verticils of peltate sporangiophores, 

 8—10 in a verticil, each bearing 4 sporangia, 

 as in other Calamarian fructifications; some of 

 the specimens shew as many as 10 successive fertile whorls, but 

 there is no sign of any bracts. Possibly all the appendages were 

 fertile, as in a recent Equisettmi and in SphenopliyUmn fertile, or it 

 may be that scattered bract-whorls occurred at long intervals, as 

 appears to have been the case in Pothocites, another fructification 

 attributed to the genus Archaeocalamites. Eqiiisetites Hemimjiimji 

 (Kids ton, 1892) from the Middle Coal-measures is another example 

 of an Ecßiisetum -\i\i% strobilus. In the absence of any specimens 

 showing the internal structure it is useless to speculate on the mor- 

 phology of these fructifications. It may however be pointed out that, 

 as the case of Splienophyllnm fertile shows, the exclusive or prepon- 

 derating presence of fertile appendages by no means militates against 

 an affinity with Sphenophyllales. 



Fig. 7. Archaeocala- 

 viites. Part of cone 

 showiug the axis iax) 

 in surface view bearing 

 superposed verticils of 

 peltate sporangiophores 

 {sj)j without bracts : sm, 

 sporangia. After Re- 

 nault. 



