CORDAITALES 183 



order than those common to Cordaitales and Coniferales; and yet 

 the latter pair are regarded as much more closely related than the 

 former pair. 



The characters in common with the Cycadales are the large j)ith. 

 the internal structure and mesarch bundles of the leaves, the general 

 structure of ovule and seed, and the swimming sperms. An inspec- 

 tion of these characters shows that they are primitive, and that they 

 may be interpreted as characters which both groups have retained 

 from some common and \'ery distant ancestry. In other words, these 

 characters are just such as might have been retained by divergent 

 lines. 



The characters in common with Coniferales are the lofty and 

 branching habit, the character of the vascular cylinder, and especially 

 the structure of the ovulate strobilus. These characters are distinctly 

 not primitive, and suggest at once that the Cordaitales are intermediate 

 between the Coniferales and the more primitive seed plants. 



The characters in common with the Ginkgoales are those shared 

 in general by the Coniferales, except the structure of the ovule and 

 seed, and the swimming sperms, which are also cycadean characters. 

 The suggested conclusion is that Cordaitales also connect the Gink- 

 goales with the more primitive seed plants, and that the reproductive 

 structures of the Cordaitales were retained by the Ginkgoales. 



LITERATURE CITED 



1. Williamson, W. C, On the structure and affinities of the plants hitherto 

 known as Stembergiae. Mem. Manchester Lit. and Phil. Soc. 14:340-358. 

 pi. 10. 185 1. 



2. Grand 'Eury, C, La flore carbonifere du Departement de la Loire. Mem. 

 Acad. Sci. 24': pp. 624. pis. j8. 1877. 



3. Renault, B., Structure comparee de quelques tiges de la flore carbonifere. 

 Nouv. Arch. Mus. Hist. Nat. II. 2:213-348. pis. 8. 1879. 



4. Bertrand, C. E., et Renault, B., Recherches sur les Poroxylons. Archiv. 

 Bot. Nord. Frances: pp. 147. figs. yg. 1886. 



5. Solms-Laubach, H., Fossil botany. English translation. 1891. 



6. Renault, B., Bassin houiller et Permien d'Autun et d'Epinac. IV. Flore 

 fossile. pp. 557. 1896. 



7. ScOTT, D. H., On the primar\' wood of certain araucario.xylons. Annals of 

 Botany 13:615-619. 1899. 



8. , Studies in fossil botany. 1900. 



