﻿1 84 



REPRODUCTIVE STRUCTURES. 



BISEXUAL1TY OF CYCADEOIDEA DACOTENS1S. 



A careful consideration of the fore- 

 going data must lead one to deem it 

 evident that quite every one of the fructi- 

 fications just described, as well as most of 

 the others borne by trunk 214, were actu- 

 ally bisexual. That a few of the ovulate 

 cones may have aborted after the produc- 

 tion of pollen, and that conversely some 

 of the sixty-odd fruits present ma}- have 

 been simply ovulate and have failed to 

 produce fertile staminate disks is possible 

 and even probable ; but there is no direct 

 evidence pointing to such a fact. Far 

 down at the base of the trunk is oue ovu- 

 late fruit of about the same size as No. 

 11 and further advanced in growth. Per- 

 haps because of its restricted position 

 such a fruit might have failed to produce 

 a staminate disk and spent all its energies 

 in ovule production, or perchance it is 

 nearly a season's growth in advance of 

 the others. As this cone must have been 

 quite below the level of the ground one 

 wonders how it would finally have been 

 fertilized, to say nothing of many other 

 bract-inclosed fruits, unless through the 

 intervention of free-swimming anthero- 

 zoids. 



It is held that none of the cones just 

 described were sufficiently advanced in 

 growth to have been fertilized by any of 

 the earlier borne pollen, unless, as in the 

 living cycads, the pollen retained its 

 vitality for a long time, several months 

 perhaps, or was slow to reach the stage 

 when actual fecundation took place. 



THE FRUITING HABIT OF CYCADEOIDEA 

 DACOTENS1S. 



Perhaps the preceding study of a long 

 series of young fruits from trunk 214 has 

 revealed no more interesting fact than that 

 all or all but a very few of its fruits are 

 uient, it being likely that most of the flow 



5. SO/ 



II 



mm 



S.50Z 



a 



Fig. 100 — Continued. The transverse series of sections cut 

 from fruit V. T. 214. Natural size. The position of 

 these sections is respectively shown by the lines I -VI, in 

 figure 100, of the accompanying longitudinal section. 



c, in sections II1I. denotes the bundle cylinder of the ovulate cone, 

 in 1V-V that of the peduncle, and in VI the peduncle trace ; a. 

 in section IV, the axillary leaf base, and in section VI the bundle 

 trace of this leaf base as seen next beneath the peduncle trace in 

 the outer cortex ; d, the basal remnants of an earlier borne hypog- 

 ynous disk, evidently staminate, and already matured and dehis- 

 cent at time of fossilization. The arrow points toward the summit 

 of the trunk — section HI, as due to an oversight, having been 

 drawn in the reverse position. 



I. Section through upper end of ovulate cone at point of greatest 

 diameter. S. 501. 



II. Section through lower half of ovulate cone, showing the lateral 

 surface fluting of the fruit due to bract appression. Most of the 

 bracts and two leaf bases appear at this level. S. 502. 



HI. Section through receptacle or end of peduncle, showing also 

 the basal remnant of hypogynous disk and the complete bract 

 series, presenting a distinct spiral succession; also four of the 

 surrounding leaf bases. S. 504. 



relatively of the same stage of develop- 

 ers produced ovules subsequent to pollen 



