316 Systematic Paleontology 



Maryland area, and these are here retained unaltered, although it is 

 very probable, as already stated, that this is too large a number. 



In view of the constantly increasing evidence of the abundance and 

 extent of variation in the cycad-like plants during the Mesozoic, it' has 

 seemed proper to adopt the siiggestion of Professor Nathorst ^ and con- 

 sider them as representing a distinct class, the Cycadophytse. Concern- 

 ing their segregation within the class we know as yet too little to estab- 

 lish natural lines of cleavage. The genus Cycadeoidea is here retained 

 in the larger group denominated the Bennettitales in contradistinction 

 to the Cycadales, which term is reserved for forms resembling the modem 

 types, as a matter of convenience and not as representing an altogether 

 •natural grouping. 



The most interesting features of the Mesozoic cycadophytes are their 

 fructifications and fruiting habits, for a knowledge of which we are in- 

 debted to Carruthers,^ Solms-Laubach,^ Lignier,* ISTathorst," and Wieland.^ 

 Among all of the five score or more species of existing cycads the dis- 

 tribution of which is shown on the accompanying sketch map (fig. 6) the 

 fructifications are of a simple and rather uniform type. The staminate 

 or pollen-producing organs have the form of a cone, the pollen sacs being 

 attached in groups to the lower surfaces of the cone scales (sporophylls) . 

 In all but one of the nine existing genera into which these species are 

 grouped the ovulate or seed-bearing fructification is also a cone, each 

 scale (sporophyll) of which bears two seeds. In the genus Gycas, how- 

 ever, a far more primitive condition exists, the ovules being borne along 

 the edges of carpellary leaves (sporophylls) which spring from the main 

 axis exactly as d.o the foliage leaves, which they greatly resemble. This 

 is by far the most archaic and fern-like method known among modern 



^ Nathorst, Beitr. z. Kennt. einiger Mesozoischen Cycadophyten, Kgl. 

 Svenska Vetens.-Akad. Handl., Band xxxvi, No. 4, 1902. 



^ Carruthers, Trans. Linn. Soc. Lond., 1870, vol. xxvi, pp. 675-708, pi. liv-lxlii. 



^ Solms-Laubacli, Ann. of Botany, 1891, vol. v, pp. 419-454, pis. xxv, xxvi. 



* Lignier, Veget. Foss. de Normandie, Caen, 1894. 



» Nathorst, Kgl. Svenska Vetens-Akad. Handl., Band xlv, No. 4, 1909, lUd., 

 Band xlvi. No. 4, 1911. 



" Wieland, loc. cit. 



