BENNETTITES. 149 



of cells which, "formed a cortical layer, arranged vertically upon 

 and extending over the entire surface of the pyriform axis." 

 In another type of specimen figured by Williamson, we have 

 a disk-shaped structure with a central depression, and split up 

 peripherally into several short and narrow segments ; this is 

 named the " carpellary disk," and towards the apex of each of 

 these rays there are said to be two small pits on the lower 

 surface. These pits are regarded as the places of attachment 

 of ovules ; but it is now generally agreed that there is no good 

 evidence for the existence of well-defined depressions which 

 could be described as marking the position of seeds. The general 

 conclusion arrived at, and expressed by a restoration of the whole 

 plant, is that the two forms of fructification are probably the 

 male and female organs of Zamites gigas ; the commoner ovoid 

 fossil being the male flower, with a pyriform axis originally 

 invested by a deciduous antheriferous tissue, and the female 

 flower being represented by the much less abundant "carpellary 

 disk," with the ovules inserted in pits towards the tips of the 

 star-like rays. 



As a convenient provisional name for these anomalous structures 

 Carruthers instituted the genus Wittiamsonia, and placed it in 

 a new tribe Williamsonece. The genus is thus defined: 1 "Stem 

 cylindrical, elongated, marked with the equal-sized, tumid, 

 rhomboidal scars of the fallen leaves. Leaves ovate-lanceolate 

 or linear acuminate, segments numerous, attached to the rachis 

 by the central portion, with small free margins ; veins numerous, 

 parallel, at the base slightly diverging into the free margins. 

 Flowers terminal, stamens surrounding a fleshy axis, ovules borne 

 on the upper surface of an orbicular laciniate spadix." 



Carruthers thus expresses himself with reference to "Williamson's 

 work: "He has introduced a clearer apprehension of the different 

 forms of the supposed organs of reproduction, by the suggestion 

 that the two kinds represent the different sexes, and by the 

 discovery of a seed-bearing spadix." 2 In the second volume 

 of his Plantes Jurassiques, Saporta considers the problem of 

 Wittiamsoma, 3 and denies the existence of any satisfactory grounds 



1 Carruthers (1), p. 691. 



2 Ibid. p. 692. 



3 Saporta, Pal. Fran9_ vol. ii. p. 53. 



