62 AN INTRODUCTION TO THE STUDY OF FOSSILS 



stem, there was a close similarity between these plants and the 

 living cycads. Some of their characters, such as their lateral 



branching and the hairlike 



and papery scales profusely 

 covering the leaf-bases recall 

 the cycadofilicales and the 

 ferns. In the structure of 

 their fruiting organs, how- 

 ever, the cycadeoids were 

 peculiar to themselves, and 

 showed an advance over the 

 other orders. They had a 

 true flower since both male 

 and female organs were borne 

 on the same axis and were 

 arranged in the manner typi- 

 cal of the later flowering 

 plants, — the angiosperms. 

 This flower (Figs. 21, 22) con- 

 sisted of a sheath of hairy 

 overlapping bracts inclosing 

 a circle of leaf-like, pollen- 

 bearing organs analogous to 

 stamens, central to which is a conical axis bearing stalked seeds, 

 the " receptacle " of higher plants. 



The seeds are often so well preserved in various species that 

 the embryo may be distinguished ; this is dicotyledonous, dif- 

 fering from that of other gymnosperms in occupying nearly the 

 whole seed. This is, however, the only order of fossil plants in 

 which an embryo has been sufficiently well preserved to be 

 studied in detail. 



In general appearance, therefore, these plants at once suggest 

 the cycads ; in the large, leaf-like stamens and certain features 

 of their pollen sacs they indicate an affinity with the ferns, and 

 in the possession of true flowers they distinctly approach the 

 angiosperms. 



Fig. 20. — Cycadeoidea jenneyana. Photo- 

 graph ( X 3) of a longitudinal section 

 through a silicified young leaf not yet 

 emerged from the bud. (From Wie- 

 lahd.) 



