XXXVII] WIELANDIELLA 465 



more slender specimens. Closely set polygonal leaf-scars cover 

 the stem for a short distance below each bifurcation and the 

 surface of the short and relatively stout peduncles of the strobili 

 (fig. 567). Though for the most part confined to the region of 

 false dichotomy, leaf-scars occasionally occur on other parts of 

 the stem. Small fronds, 7 — 8 cm. long, agreeing closely with 

 Anomozamites minor Brongn., occur in the same beds at Bjuf, 

 and the striking resemblance between their long linear and winged 

 petioles and the transversely striated bracts enclosing the strobili 

 of Wielandiella amply justifies Nathorst's conclusion that Wte- 

 landiella bore fronds of the Anomozamites form^. Small scars 

 marking the position of bracts occur immediately below each 

 strobilus and occasionally form narrow zones between the larger 

 foliage leaf-scars. The strobili are met with in two forms repre- 

 senting two states of preservation and, probably, different ages. 

 In one form the strobilus consists of a small pyriform axis separated 

 from the peduncle by an annular swelling characterised by parallel 

 striations (fig. 567), the so-called palisade-ring. From this ring 

 Nathorst obtained many microspores scattered and in groups on 

 the surface of short sporophylls, 2-5 — 3 mm. in length. It is 

 these sporophylls which form the parallel striations; they occur 

 as a circle of rather broad linear organs with irregularly toothed 

 distal ends and an epidermis of papillose cells. The oval micro- 

 spores, 32 — 42/x long, vary in size and, as Nathorst says, this 

 may indicate immaturity. The precise mode of occurrence of 

 the spores has not been ascertained, but they were probably 

 produced in sporangia on the surface of the small microsporophylls. 

 These strobili have in all probability lost the female organs which 

 were borne" on the pyriform axis, and the inference is that the 

 strobili were protogynous. Thomas^ compares the ring at the 

 base of the flower-axis from which spores were obtained by Nathorst 

 to the whorl of microsporophylls of Williamsoniella, but in 

 Wielandiella the sporophylls are greatly reduced and possibly 

 functionless. Wielandiella may be intermediate between the 

 bisexual Williamsoniella and the unisexual Williamsonia scotica. 

 In the second form of strobilus the pyriform axis is hidden and 



1 For figures of the stem and flowers, see Nathorst (02); (09). 



2 Thomas (15^). 



S. Til 30 



