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REPRODUCTIVE STRUCTURES. 



bracts, the peduncle, and, in particular, of all the basal portions of the cone, is quite 

 identical in all these mature ovulate forms and the present functional bisporangiate 

 axis. The conclusion is therefore a plain one, that thus far no clear indication of 

 dioecism has yet been observed in any of the present series of trunks, although, as 

 will presently be recounted, it should not be overlooked that some very small 

 cones borne by cycad trunk 131 are simply ovulate. Obviously enough it is under 



Fig. 87. — Cycadeoidea dacotensis. 



Semi-diagrammatic sketch of bisporangiate strobilus, cut longitudinally, with one frond folded and one arbitrarily expanded to 

 the right. At the center is the apical cone formed by the elongate and conical receptacle closely invested by a zone of young 

 and short-stalked ovules and interseminal scales. The single unexpanded frond of the hypogynous staminate disk to the 

 left shows the reduced pinnules bearing the densely packed synangia folded inwards between the ascending and descending 

 limbs of the rachis. The expanded frond is shown as if twisted into an approximately dorsal view. Exteriorly are several 

 of the enveloping hairy bracts. About natural size. (Compare with figures 54 and 70.) 



such circumstances difficult to say, on the basis of isolated strobili, to what extent 

 the parent trunks may have been bisexual or unisexual, or certain species monoe- 

 cious, or certain others dioecious. The structures present clearly permit or favor 

 the utmost variation in these respects. (The presence of disks is further considered 

 in connection with the subject of the more mature ovulate cones in Chapter VI, 

 pages 114 and 130, as well as in Chapter VIII on young fructifications.) 



