66 MORPHOLOGY OF GYMNOSPERMS 



Ptolophyllum (from India), etc. There is more or less confusion as 

 to generic limitations, and the names cited are not applied uniformly 

 by all writers. For example, the Cycadeoidea Buckland of American 

 authors is a synonym of Bennettites Carruthers of European authors, 

 but it is convenient to use the two names at present to distinguish 

 American and European material of the genus. To the morphologist 

 the group is a very consistent one, and at this stage of knowledge 

 the differences among genera and their nomenclature are of minor 

 importance. 



I. The vegetative organs 



The habit of Bennettitales was much more diversified than that 

 of existing Cycadales. The tuberous type of trunk (fig. 55) prevails 

 among the known forms, and short columnar trunks also occur, both 

 of which types of body are familiar among cycads; but there are 

 also tall and slender forms, as Williamsonia gigas (fig. 56); and 

 branching forms occur, commonly resulting in multiple crowns (as 

 in Dioon and Zamia), and in the case of Williamsonia angustifolia 

 {Anomozamites, 17), a form which flourished in the early Triassic 

 of southern Sweden, and probably represented in Mexico (30), the 

 body was slender and widely branching (fig. 57). The recently 

 described (31) Wielandiella, from the Jurassic beds of England, is 

 also slender and widely branching. The largest specimens are 

 from the Black Hills region, huge tuberous bodies of Cycadeoidea 

 occurring over a meter in height and more than half that in diam- 

 eter; while the species of Cycadella from the Freezeout Hills are 

 said to average only 35 cm. in height and 20 cm. in diameter. 

 The columnar trunks from the United States are over a meter in height, 

 and in the case of Cycadeoidea Jenneyana such trunks reach a height 

 of three to four meters. 



The compact forms are covered by an armor of closely imbricated 

 persistent leaf bases, and a crown of cycad-like leaves. Among these 

 leaf bases numerous short, axillary branches are wedged, each bear- 

 ing a terminal strobilus that projects more or less beyond the armor 

 (fig- SS)- These numerous axillary, cone-bearing dwarf shoots, 

 borne on a monopodia! trunk, are in sharp contrast with the habit 

 of Cycadales, whose sympodial trunks bear a succession of terminal 



