72 MORPHOLOGY OF GYMNOSPERMS 



Anomozamites are leaves differing from those of any living cycads. 

 The mature fronds of Cycadeoidea ingens are estimated (22) to have 

 attained a length of three meters. The leaves of the slender and 

 widely branching Williamsonia angustifolia {Anomozamites) seem 

 to have occurred in clusters at the ends of branches and at the forks, 

 each cluster surrounding a small terminal strobilus (fig. 57), and 

 composed of leaves which were linear in general outline and pinnate 

 with short, broad lobes. 



The absence of scale leaves from the crown of the tuberous and 

 columnar forms, alternating with the foliage leaves, has been 

 remarked; but scale leaves are related to strobili. Among Cycadales 

 the terminal strobili necessarily involve the association of their envelop- 

 ing scales or bracts with the crown of foliage leaves; among Ben- 

 nettitales the lateral position of the strobili prevents any association 

 of their scale leaves with the foliage of the crown, and such leaves 

 or bracts form the characteristic husklike covering of the strobili. 

 Among Cycadales the enveloping bracts are much more open, but 

 they are as definitely related to individual strobili as among the 

 Bennettitales. 



2. The spore-producing members 



THE STROBILUS 



Perhaps the most important result of Wieland's investigations 

 (7, 8, 9, 16, 22) was the discovery of the bisporangiate character of 

 the' strobilus. At first it was supposed that this might be an excep- 

 tional condition in the group, but it has now been found in so many 

 genera and species that it is known to represent the general condition. 

 In a recent examination of certain species of Bennettitales from the 

 Jurassic beds of England, Nathorst (31) concludes that two species 

 of Williamsonia and Cycadocephalus Sewardii bore monosporangiate 

 strobili, but the general occurrence of bisporangiate strobili seems 

 assured. Wieland found bisporangiate strobili not only in numerous 

 sections of American material, but examined the best known European 

 forms {Cycadeoidea etrusca, C. Reichenbachiana, Williamsonia gigas, 

 and W. angustifolia) and found bisporangiate strobili in all of them 

 (26). The microsporophylls (stamens) have disappeared when the 

 seeds are mature, but in seed-bearing strobili. the former position of the 



