The Present Eositiou of Palaeozoic Botany. 



159 



through a considerable part of the internode above, and then bends 

 downwards and outwards to enter the corresponding sporangiophore. 

 This fact is of the greatest interest, as it tends to show that the 

 sporangiophores, though so widelj^ separated from the bracts, are in 

 reality their ventral appendages, just as in the case in the fructifica- 

 tions of Sphenophyllales. 



The bracts of each verticil may be 

 gamophyllous or polyphyllous ; in either 

 case theii' erect limbs protect the sporangio- 

 phores above them. The sporangiophores 

 themselves are peltate, each bearing four 

 sporangia, as in Cheirostrobus. In certain 

 species, as in C. Binneyana, specimens of 

 which are extremely common, there seems 

 to be no doubt that homospory prevailed, 

 while in others, as in C. Casheana, there is 

 a marked differentiation of microspores and 

 megaspores, occurring in distinct sporangia, 

 though sometimes on the same sporangio- 

 phore. The abortion of certain spores which 

 has been observed both in the homosporous 

 species and in the megasporangia of the 

 heterosporous C. Casheana, may throw some 

 light on the origin of heterospory in this 

 group of plants. 



Fig. 6. Palaeostachya. Dia- 

 gram of cone in radial section ; 

 ax, axis, which hears verticils 

 of hracts [br) with peltate 

 sporangiophores (s/>) in their 

 axils, sm, sporangia. After 

 K e n a u 1 1. 



Palaeostachya, the species of which are 

 less common in the petrified condition than 

 those of Calamostachys , differs essentially 

 from that genus in the position of the 

 sporangiophores, which, instead of Ijàng 

 midway between the verticils of bracts, 

 occupy an apparently axillary position, 

 immediately above the subtending sterile 



whorl (Fig. 6). One might thus be tempted to believe that in this 

 type of cone there was a nearer approach to the conditions in the 

 Sphenophyllales, the sporangiophores showing an evident relation to 

 the bracts of the snbjacent verticil. The case however appears not 

 to be so simple. The British species, Palaeostachya vera, originally 

 described by Williamson, is now in course of more detailed in- 

 vestigation by Mr. Hick ling of Manchester, who kindly allows me 

 to quite some of the results of his unpublished observations. The 

 anatomy of the axis is of the ordinary Calamarian type, except that 

 the vascular bundles are approximated in pairs, "The sporangiophores 



