I. m 



G. R. Wiehiiid — Williamso7iian Tribe. 



several genera arc known, and the necessity for careful quarry 

 work followed by approved laboratory methods understood, we 

 may not only hope to find better conserved disks and whorls of 

 the types already sparingly observed, but those of hypothetical 

 reduced forms. In fact we even get the clearer suggestion of 

 family differentiation in the more diffuse organs of the stami- 

 nate series, since lax-spiral ancestral types of ovulate fructifica- 

 tion or later reduced types have not yet been clearly connected 

 with cycadophytans — the ovulate strobili so far determined 

 being strictly confined within the same narrow structural limits 

 as in the parallel (Jycadeoidea ovulate series. 



Fig. 16. 



Fig. 16. Early illustrations of Williamsonian staminate disks. (About 

 half natural size.) 



A. So-called " earpellary disk " as restored by Williamson ; — now referred 

 to Williamsonia bituberculata, cf. Nathorst's restoration, fig. 17. x 2/5. 



B. Williamsonia gigas from the Rajmahal Hills as figured by Feistmantel. 



Referring at once to the illustrations of typical staminate 

 fruits, in lieu of further description, the known types of such 

 fructification in Williamsonia and the nearest related forms 

 are given in the subjoined table. 



List of Staminate Whorl and Disk Species of Williamsonia 

 and Related Forms. 



(Provisionally grouped.) 



Cycadeoidea. — Various species of bipinnate frond disks. 

 Cycadocephalus Sewardi Nathorst (25). — The type of a 



family anciently related to Williamsonia. Has tetrahedral 



fern-like microspores borne on large deeply cleft disk of 



15 ± sporophylls. 

 Williamsonia spectabilis Nathorst. — Disk 15 ± bipinnately 



parted fronds. 

 Williamsonia setosa Nathorst. — Disk of 18 ± parted fronds. 

 " whitbyensis Nathorst. — Disk pinnately 15 — 



cleft. 



(-4) 



(C) 



