44 GYMNOSPERMS 



Williamsonia gigas was tall and slender, while W ilUamsonia (Ano- 

 mozamitcs) angustifolia was slender and profusely branching. 



The Williamsonia {Anomozamites) angustifolia type of stem shows, 

 on the outside, what the Dioon type of stem shows on the inside; for 

 the outwardly unbranched stem of Dioon is really profusely branched 



FiCf. 37. — Cycadeoidea wielandii: upper part of a trunk found near Hermosa, South 

 Dakota: some of the strobili arc project inR and some have fallen out, leaving cavities 

 which arc dark in the illustration. The height of the specimen is 54 cm. — From a photo- 

 grapli by Thikssen. 



on the inside (fig, 38). If material of this Williamsonia were avail- 

 able, just at the base of the terminal cone we should expect to find 

 newly formed meristems which would give rise to branches. Each of 

 these branches, with its leaves, would soon be terminated by a cone, 

 at the base of which a new meristcm would form, and so a profusely 

 branched plant would be developed. It should be noted that the 



