BENNETTITALES 43 



phylliim, Otozamites , and Williamsonia. Many of the species are new. 

 While the impressions of leaves and fruits are abundant and wonder- 

 fully clear, there are no silicified specimens to show the internal 

 structure. 



In England and Scotland well-preserved specimens have been 

 found in various horizons in the Triassic, Jurassic, and Cretaceous. 

 Germany, Belgium, Poland, Russia, Italy, and the Isle of Wight 

 have yielded material, and India has long been a famous fossil cycad 

 locality. 



LIFE-HISTORY 



Most of the material from which the internal structures of the 

 CycadofiHcales have been studied is calcified. In the Bennettitales 

 the material is silicified. In making peels, hydrofluoric acid must be 

 used, and cutting sections is more laborious; but the harder surface 

 allows a higher degree of polish, and very satisfactory studies, and 

 even photomicrographs, can be made from cut surfaces without any 

 balsam or cover. 



The stem. — If any form can be considered typical of the Bennetti- 

 tales, it is the unbranched stem with a crown of leaves at the top; 

 but branching was probably as common as in the living cycads. The 

 axillary strobili gave the stems a very characteristic appearance so 

 that they could not be mistaken even for those Cycadales in which 

 the strobili are axillary (fig. 37). 



The tuberous habit was common, and this, with frequent branch- 

 ing, gives the specimens a striking resemblance to the branching 

 plants of Zamia. The stems and branches, which are so similar that 

 it is often difficult to determine which is the main stem and which are 

 the branches, are usually as much as 15 cm. in diameter, and speci- 

 mens often reach a diameter of 25-50 cm. The branching tuberous 

 forms are not very tall, usually not exceeding half a meter. Some 

 columnar forms, which are not likely to be branched, have reached a 

 meter in height. The tallest on record is Cycadeoidea gigantea (Sew- 

 ard), 1. 18 M. high and about one-third that figure in diameter. 

 The smallest known specimen is Bennettites scotti, 8.5 cm. in height 

 and about two-thirds as much in diameter; this, however, was prob- 

 ably a bud from a larger specimen. 



