﻿114 REPRODUCTIVE STRUCTURES. 



a transverse section from the base of a most beautifully conserved peduncle is 

 shown in photograph i, plate xxxi. 



The pithy ground tissue of the lower portion of the peduncle is not as a rule 

 well preserved, but has given rise to characteristic mineralization and coloration, as 

 have most of the tissues failing of exact cell differentiation. In the lateral or cor- 

 tical portion of the peduncle, beneath the bases of the bracts and the annular disk 

 insertion described below, and finally in nearly all that upper portion of the peduncle 

 which expands into the convex receptacular region, the ground-tissue cells gradually 

 assume a more elongate form, as much or more than two or three times as long as 

 broad, and are very uniformly cross-lined or scalariforin ; these scalariform cells 

 continue with further increase in length into the bases of the bracts as their 

 ground tissue, and in modified form even into the peripheral and terminal por- 

 tions of the interseminal scales of the fruit. 



Evidence indicating former presence and dehiscence of liypogynous disks.- — It is 

 of fundamental importance to note that in all these strobili, above the lateral bract- 

 bearing surface of the peduncle and just beneath the terminal ovulate cone, there is 

 an annular offset or shoulder with more or less distinct traces of some earlier borne 

 and dehiscent or else abortive or wilted disk. This disk or zone of annular growth 

 is thus seated on the receptacle above the bracts, but in relatively the same manner 

 on the same semi-woody groundmass of scalariform cells as the bracts. Moreover, 

 bundle strands pass out to it from the woody cylinder of the peduncle, as may be 

 seen in photograph 2, plate xxxi, the structure plainly indicating a bundle system 

 entering a dehiscent annular growth or former staminate disk. (The photograph 

 cited as showing the dehiscent disk bundle supply is from the region marked .S in 

 photograph 2, plate xxiv, of the same cone. After giving off these disk strands 

 the cylinder of the peduncle extends a short distance farther and then anastomoses 

 in the convex parenchymatous receptacle, on which are seated the seed pedicels 

 and scales, the anastomosing system thus formed being more prominent in all 

 cones with short than in those with more elongate receptacles.) 



The insertion line or shoulder-like offset just described is more or less distinct 

 in all ovulate strobili yet examined from the Black Hills, and is indicated (by S) in 

 many text-figures and photographs of the plates. In many cases where it is 

 reasonably certain that, as in some of the fruits of cycad 214, a staminate disk has 

 just been shed, the shoulder is prominent and, as will be described later in other 

 forms, conserved basal parts of shed or wilted disk may actually remain. In some 

 other cases the liypogynous annular shoulder is much less noticeable, and there 

 seems good reason to believe that the fruit is simply ovulate. But the condition in 

 the great majority of the cones thus far examined is such that one is forced to the 

 conclusion that all the known Cycadeoidere are descended from bisporangiate forms, 

 and that of all the considerable number of fruits of Cycadeoidca and Bennettites 

 Gibsonianus, or allied species, far the larger portion were actually bisporangiate and 

 discophorous. That this conclusion has not hitherto been reached from actual 

 evidence, and but rarely suggested in modified form by others, must be due to the 

 fact that there have been available only sections showing but imperfectly, for the 



