SPHENOPSIDA 97 



suggested that the two genera merge into one another.®^ 

 Certainly the sterile and fertile appendages of C. bicephalum 

 (Figs. 15C and 15D) were very similar to those of Hyenia, 

 the chief difference being that the fertile appendages of the 

 former forked more profusely and bore twelve sporangia, 

 instead of three or four, as in the latter. The lateral appen- 

 dages of C. primaevum are said to have been much simpler, 

 forking only once, and the sporangiophores are said to have 

 borne only two sporangia; the way in which they were 

 restricted to special fertile branches may represent early 

 stages in the evolution of the strobilus, which is so character- 

 istic of later sphenopsids. 



Little is known of the internal anatomy of the Hyeniales, 

 but in Calamophyton there are indications of a triangle of 

 pith surrounded by tracheids with reticulate or scalariform 

 thickenings; it is also suggested that there may have been 

 some degree of secondary thickening. 



Sphenophyllales 



This group first appeared in the Upper Devonian and per- 

 sisted until the Lower Triassic, remains of stems as well as of 

 leaves being referred to the genus Sphenophyllum. Many 

 species are known, all of which are characterized by the 

 whorled arrangement of the leaves, usually in multiples of 

 three at each node (Fig. 15K). The stems were usually very 

 delicate, in spite of secondary thickening, for they seldom 

 exceeded i cm in diameter. Presumably, therefore, they 



branching of sporangiophore. Cheirostrobus pettycurensis : i, 

 sporangiophore and bract. Sphenophyllostachys (= Bowmanites) 

 fertilis: J, reconstruction of part of cone. Sphenophyllum cunei- 

 folium: k, reconstruction; l, stele; m-o, leaves. Sphenophyllo- 

 stachys Dawsoni: p, part of cone in l.s.; Q, part of cone in t.s. 

 Sphenophyllostachys Roemeri: r, part of cone in t.s. 



(a, after Ananiev; b, Krausel and Weyland; c, d, Leclercq and 

 Andrews; e-h, j, Leclercq; i, Scott; k, Smith; m-o, Jongmans; 

 p-R, Hirmer) 

 D 



