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VEGETATIVE FEATURES. 



present. Lastly there is present with great regularity in every cell of the ground 

 tissue over large areas of the medulla of this same trunk 393, a single and con- 

 spicuous dark-yellow body with a nearly black mass at its center, believed to be the 

 cell nucleus with perchance the nucleolus. (See fig. 41, d). It is of interest that 

 Seward observed markings in the medulla of Cycadcoidea gigantca which were like- 

 wise suspected to be nuclei. There 

 are, of course, in some of the cells 

 other more or less vague markings 

 as the result of various odd causes, 

 which might be confused with what 

 are believed to be the cell nuclei. 

 The exigencies attending nuclear 

 preservation must certainly be great, 

 since the case of C. gigantea is the 

 only recorded instance, aside from 

 the present, where such preservation 

 has even been suspected ; but the 

 fact is that over considerable areas 

 precisely the appearance is presented 

 that the writer has observed in sec- 

 tions of existing cycads showing the 

 nuclei, and he believes the bodies in 

 question to be fossil nuclei. Since 

 these bodies present such a very 

 regular appearance over considerable 

 areas of the ground tissue, and are 

 not found as a rule on any particular 

 side of the cell, the greater difficulty 

 is involved in any other explanation. 

 They may, therefore, be considered 



X/05 



Fig. 43. — Cordaites Newberryi. 



Tangential section from trunk. Upper Devonian of Indiana. 

 X 105. 



the first fairly clear instances of silicified nuclei. 



CYCADEOIDEA JENNEYANA AND C. INGENS. 



The trunks from the Piedmont-Black Hawk locality of the Black Hills region 

 referred to Cycadeoidea Jenneyana exhibit, in addition to other special features, 

 both vegetative and reproductive, the heaviest growth of wood and the most 

 advanced degree of polyxylism yet observed among either existing or fossil cycads.* 

 In fact, the polished section of the lower end of a basal cylindrical segment of a 

 trunk, probably referable to C. Jenneyana and photographed on plate xrv, reveals a 



* Taken all in all, these features are of generic value. If they are finally found to occur in Buckland's 

 original types of Cycadeoidea, then the genus Benncttiles is perfectly valid, although for other reasons 

 than those that have been hitherto assigned. If, on the other hand, the Buckland specimens in the main 

 agree with Bennettites, so called, and it is here deemed a strong possibility that they do, the name Ben- 

 nettites is invalid, and the American specimens referred to C. Jenneyana and C. ingens, together with 

 the magnificent Isle of Portland trunk C. gigantea Seward, constitute a generically distinct group. 



