kidston: the floua of the carboniferous period. 203 



Annularia Sternberg contains those forms with whorled, single- 

 nerved lanceolate leaves, widest near the centre like Annularia 

 radiata Brongt. (Plate XXXVII., fig. 2), or with spathulate leaves 

 like Annularia sphenophylloides Zenker, sp. (Plate XXXVII., 

 fig. 1). The leaves unite at the base and form a xQvy narrow 

 collar round the stem. 

 Fructification of Calamites. 



The fructification of Calamites consists of narrow linear cones, 

 attaining in some species a few inches in length, though in most 

 cases they are of smaller size. The arrangement of the sporangia 

 in many of these cones is still unknown, but of some a \ery 

 complete knowledge is possessed. For their reception several 

 genera have been founded, as hitherto it has been generally im- 

 possible to refer them to their parent stems. 



The more important of these genera may be briefly described. 

 Calamostacuys Schimper. (Plate XXXVI. , fig. 2). 



The cone is composed of alternating whorls of barren leaves 

 or bracts and sporangiferous scales. The basal portions of the 

 bracts unite to form an almost horizontal collar which surrounds 

 the axis, while the free parts of the bracts rise up almost at 

 a right angle, the whole forming a saucer-like structure. Between 

 each of these barren whorls is a fertile whorl. This consists of 

 slender pedicels or sporanglophores, which spring from the axis 

 at riglit angles and terminate in peltate shields, on the inner 

 surface of which are borne four sporangia. Both homosporus 

 and heterosporous cones occur in Calamostachi/s. 

 Pal.«ostaciiya Weiss (Plate XXXIV., fig. 5; Plate XXXVI., 

 fig. 3. Palceostachya pedunculata Williamson). 



The cones placed in Faloiostachya differ from those of 

 Calamostachys in the sporangiophores springing from the axis 

 immediately above the axils of the bracts and forming with the 

 axis an angle of about 45 degrees. 



For cones possessing the general appearance of Calamostachys 

 and Palceostachya, but in which the arrangement and position 

 of the fertile whorls are unknown, the genus Volkmannia Sternb. 

 may be conveniently employed. 



