BENNETTITALES 



67 



strobili. A jjossible relation between the two is evident when it is 

 remembered that in reality the apparently terminal strobili of Cyca- 

 dales are borne on a succession of branches which build up the sym- 

 podial trunk. If the conc-bcaring branches of Bennettitales were 

 restricted more and more to the tip of the axis, the cycad condition 



Fig. 55. — Cycadeoidea Wielandii: upper part of a large trunk found near Hermosa, 

 South Dakota; numerous strobili i)roject more or less through the armor; the dark 

 circular holes are cavities from which strobili have fallen; height of specimen, 54 cm. — 

 From photograph by Thiessen. 



might follow. In fact, there are cases which may be interpreted as 

 showing this tendency among the Bennettitales, and occasionally 

 cycads develop lateral groups of strobili, as in Ence phalartos (p. 121). 

 The restoration of W illiamsonia gigas (4), from the Lower Oolite 

 of the Yorkshire coast, long known as Zamia gigas (i, 3), shows 

 (fig. 56) a slender columnar shaft bearing a crown of large leaves, the 



