232 ME. HAMSHAW THOMAS ON THE FOSSIL FLORA OF [June 1913, 



bends over they seem to lie in rows of four or five, but decrease 

 again in number on the terminal over-arching parts. 



The synangia of each row appear to have been borne on slender 

 stalks which are sometimes seen, but the sandy nature of the 

 matrix makes the structure rather indefinite in places. These 

 stalks seem to have been given off on each side of the central 

 portion of the sporophyll, and may be regarded either as lateral 

 lobes of this organ, or possibly as arising as part of a pinnate 

 structure like the microsporophyll of Bennettites, which is adnate 

 with the broad structures hitherto termed sporophylls. The exam- 

 ination of the specimens favours the former view, but in few cases 

 is the origin of the synangium-bearing branches clearly seen. The 

 latter view is not based on any actual evidence, but may be advanced 

 to homologize the present structure with the American specimens 

 of Bennettites, where whorls of free bracts occur outside the narrow 

 segments of the microsporophylls. Though the attachment of the 

 lateral branches to the sporophyll is not very clearly seen, in some 

 places they seem to be given off from the centre of the sporophyll. 

 In other places (see PI. XXIV, figs. 1 a & lb) they appear as 

 slight projections on the side of the main sporophyll at intervals 

 of about 7 mm., but are seldom sufficiently definite to be considered 

 as more than indications of the structure. In one case, however, 

 near the apex of a sporophyll the projection is of the nature of 

 a small lateral lobe about 7 mm. long, rounded at the end and 

 bearing one or two synangia (see PI. XXIV, fig. 1 6). 



The synangia appear to be produced on each side of some of 

 these lateral segments. By careful dissection of part of the 

 sporophyll, it would seem probable that towards the apex the 

 inward projecting lobes occurred on both of its margins. 



Whatever may have been the method of production of the 

 synangia of Williamsonia spectabilis, this form serves (as Prof. 

 Xathorst believes) as a valuable connecting-link between the type 

 of microsporophyll seen in Bennettites (Cycadeoidea), where the 

 sporophyll is a reduced pinnate structure, and the Williamsonia- 

 ivhitbiensis type, where the sporophyll is undivided, and bears a 

 double row of synangia on its surface. The latter type is also 

 seen in Weltrichia and Cycadocephalus 1 according to Prof. Xathorst, 

 and in my new Yorkshire form Willi amsoniella. A rather curious 

 impression has also been found in the sandstone, which is of the 

 form shown in fig. 3 (PI. XXIV). "We can only form a conjecture 

 as to the nature of this structure, but it appears to have probably 

 been a separate young microsporophyll of a ' flower ' of the type 

 described above. The projecting lobes of the sporophyll are well 

 seen, but no indications of synangia can as yet be made out. The 

 occurrence of this single sporophyll, if such be its nature, leads 

 us to wonder whether the sporophylls could have been free when 

 young and have become united when older. 



1 Nathorst (12 1 ) p. 10. 



