﻿OVULATE CONES. I 37 



RESUME. 



The best known of the short axillary seed-bearing fruits of the Cycadeoideae 

 have hitherto been those of Bennettites Gibsonianus from the Lower Greensand of 

 the Isle of Wight, and B. Morierei from the Oxfordian Jurassic of Normandy. In 

 addition, during the past seventy-five years, many casts and imprints of the ovulate 

 cones of various species of Williamsonia have been found on the Yorkshire coast, as 

 well as in other European localities. Noteworthy, too, is the occurrence of these 

 cones accompanied by foliage in the Jura of India (as figured in Chapter I) ; also in 

 the Trias of Southern Sweden, as so fully described by Nathorst. Such fossils 

 have in a most interesting manner amplified our knowledge of the cones with their 

 structure so wonderfully conserved. Conversely, the latter make possible the exact 

 interpretation of imprints. 



In the present chapter four or more new species of cycadeoidean cones are 

 described as borne in great profusion by various silicified trunks from the Black 

 Hills fossil cycad localities, the richest thus far discovered. As based on this 

 extensive new material many habitus details are added and a redescription of 

 strobilar organization is given, in which the hitherto little or unknown features 

 are described, especially the complete peduncles (with the cortical bundle system), 

 the entire bract series, and the hypogynous annular shoulder indicating the earlier 

 attachment of a dehiscent staminate disk in all of the larger seed-bearing cones. 

 It is concluded that fructification was a culminant event in the life of most of the 

 trunks, since most either bear few fruits or young series of fructifications, while 

 the seed-bearing cones approaching maturity often occur in very large numbers 

 over all the lateral surface of the trunk and such branches as are present, with but 

 few or no old peduncles or immature forms. It is also made clear that while a 

 bisexual strobilus is primarily indicated, the form of fructification is precisely the 

 one capable of most varied phases of moncecisin and dioecism, which of course 

 can not be determined short of the study of numerous fruits from different trunks 

 of the same species. It should also be definitely stated that while dioecious and 

 monoecious or mixed bisexual forms are suspected to be present, no such have 

 actually been determined. The dicotyledonous embryos of the Cycadeoidese — the 

 only ones known in any extinct group of fossil plants — are also present in some 

 of the American specimens. Furthermore, pre-embryonal stages have beeii observed 

 in the latter, which exhibit a partial agreement with Ginkgo, in which there is no 

 intervention of suspensors in the formation of the embryo from the homogeneous 

 mass of large-celled tissue constituting the proembryo or protocorm. Of supreme 

 interest is the fact that there is probably at hand material which, when once fully 

 elaborated, will disclose the main outlines of embryogeny in the Cycadeoidese. 



