part 1] 



PBOCEEDI^sTGhS OF THE GEOLOGICAL SOCIETY. 



Vll 



shomng rootlets penetrating the leaf -bases of a petritied specimen 

 (represented by a section in the Geological Department of the 

 British Museum — Natural History). These roots probably belong 

 to BenneUites saxhyanus ; the}^ are covered with wonderfully- 

 petrified root-hairs, running uncollapsed through the silica matrix. 

 They raise interesting questions concerning the possible chemical 

 conditions of the infiltration of the silica. Illustrations were also 

 exhibited of the famous complex ' flower ' and cone-structures, and 

 of Wieland's brilliant restorations of the same. 



Microphotographic slides were exhibited of the seed-cone of an 

 interesting unpublished new species from the British G-ault. This 

 is beautifully petrified, and adds to our knowledge of the finer 

 anatomy of the seeds and associated structures. It is also the 

 largest cone of the Bennettitales yet known, though it occurs in 

 the Gault, by which time the group appears to have begun rapidly 

 to die out. 



The following table illustrates the distribution of a few of the 

 most interesting representatives of the Bennettitales (including 

 the cohorts Bennettiteae and Williamsonese) : — 



Upper Cretaceous. 



Very fragmentary and uncertain records ; apparently 

 the group is nearly or quite extinct. 



Middle Cretaceous 

 Gault. 



The new large-sized seed-cone. 



B.morierei $ (? described originally from the Jurassic). 



Lower Cretaceous : Well-petrified trunks with fructifications. 



Lower Greensand. B. gibsonianiis (type-species of the Bennettiteae). 



Throughout 

 these periods 



B. maximus. 

 Potton Sands. Trunks, e.g. Colynibetes edwai-dsL 



Wealden. Trunks (casts and petrifactions), 



foliage. 

 jB. saxhyanus. 



Jurassic : Purbeck. Trunks (casts and semi-petrifac- 

 tions). 

 Buckland's original Cycadeoidea 



spp. 

 C. gigantea. 



Trunks, pith-casts, etc. Much 

 foliage of various types. Wil- 

 liamsotiia gigas and other fruit- 

 impressions. 

 W. scotica. 



Williamsoniella coroaata. ~) E-ich impressions in 

 I Mexico of William- 

 r sonia and many 

 J foliage genera. 

 Wielandiella angustifolia and foliage. 



Oolites. 



Lias. 



Rhaetic. 



in America, 

 trunk-remains 

 very abun- 

 dant, often 

 petrified and 

 with fructifica- 

 tions, parti- 

 cularly from the 



Black Hills, 



South Dakota, 



and Maryland, 



C. jenneyana, 



C. ingens, 



C. wielandi, etc. 



Foliage and Williamsonia- 

 fruits (India). 



This group is by far the most characteristic of all the plants of 

 the Jui-assic and Lower Cretaceous, during which periods its 

 distribution was almost world-wide. It was locally, if not univer- 

 sally, dominant, and was the most highly evolved plant-group of 

 the epoch of which we are cognizant. 



