BENNETTITALES 



79 



erous region only interseminal scales occur; above this there are usually 

 five or six scales packed around each seed pedicel (fig. 65). The 

 scales are slender (filiform) at base and gradually thicken upward 

 in prismatic form to the seeds, where the faces are hollowed to receive 

 them. Above the seeds the 

 scales enlarge again and their 

 tips form a complete mosaic, 

 perforated only by the micro- 

 pylar tubes. 



In the group of species 

 with more or less elongated 

 receptacles, as Cycadeoidea 

 dacotensis (fig. 66), the nu- 

 merous scales and pedicels are 

 relatively short and of uniform 

 length, so that in a young stage 

 the conical tip of the axis, as 

 WiELAND suggests, appears 

 like a brush. 



There are two interpreta- 

 tions of these scales and pedi- 

 cels. LiGNiER (25) maintains 

 that the scales are bracts in 

 whose axils the pedicels appear; 

 and that therefore the pedicel 

 is an axial structure bearing 

 an ovulate "flower" reduced 

 to its lowest terms. This view 

 necessarily regards the strobilus 

 of Bennettitales as an "inflo- 

 rescence," which, in so far as 

 it means a compound (branching) strobilus, is represented among 

 gymnosperms by the ovulate strobih of certain of the Pinaceae and 

 by both strobili of the Gnetales. The same investigator (19) has 

 also satisfied himself, by an examination of Bennettites Morieri, that 

 in all the scales which enter into the composition of the strobilus the 

 terminal enlargement is due to hypertrophy and is not a reduction 

 stage. 



Fig. 63. — Bennettites Gibsonianus: dia- 

 gram of seed-bearing strobilus; the seeds, 

 each containing a dicotyledonous embryo, 

 are borne on long pedicels; between the 

 seeds are the interseminal scales with dilated 

 ends; surrounding seeds and scales are 

 overlapping bracts. — Modified by Scott (io) 

 after Solms-Laubach (5) and Potonie 

 (6a). 



