56 MORPHOLOGY OF GYMNOSPERMS 



as far back as any of the Primofilices. That the group arose from 

 fernlike ancestors seems evident from their foHage, anatomy, and 

 microsporangiate structures (6i). We are confronted by two alter^ 

 natives: either the CycadofiHcales were derived from the Primo- 

 filices, or the two groups had a common origin far back in the 

 Paleozoic. It would seem to make very little difference which alter- 

 native is selected, for either would explain the similarities, and neither 

 can be proved. 



Microsporangiate structures. — ^The resemblance of the micro- 

 sporangiate structures of all the cycadophytes (see below) to the sori 

 and synangia of ferns is so evident that further statement seems 

 hardly necessary. Kidston (64) has called attention to the resem- 

 blance between the sorus known as Dactylotheca and the microspo- 

 rangiate sorus known as Crossotheca. There is the same relation to the 

 pinnules, the same radiate arrangement of the sporangia; and if the 

 sporangia of Dactylotheca were extended beyond the margin of the 

 pinnule into a free tip which bent downward, the Crossotheca type 

 would be reached. Of course, Dactylotheca may prove to belong to 

 the Cycadofilicales, but it represents a soral structure that belongs 

 to undoubted ferns. The terminal sporangial tufts of Botryopteris 

 and of Zygopteris are easily related to the Calymmatotheca type of 

 terminal synangium; while ordinary synangia borne upon the com- 

 paratively unmodified foliage leaves of Cycadofilicales (and even 

 Bennetti tales) are exact duplicates of the synangia of Paleo-Marat- 

 tiaceae and modem Marattiaceae. In microsporangiate structures, 

 therefore, the Cycadofilicales, and even the cycadophytes, can hardly 

 be regarded as above the level of ferns. 



MEGASPORANGLA.TE STRUCTURES. — While the vascular anatomy 

 and microsporangiate structures of the Cycadofilicales may be shown 

 to be so closely related to the corresponding structures of the Primo- 

 filices and Marattiaceae that a phylogenetic connection seems clear, 

 no such claim can be made for the seeds. As Scott has said (67), 

 " the discovery of seeds [of Cycadofilicales] hardly touches the problem 

 of the origin of gymnosperms, for the discovered seeds are well devel- 

 oped, on the cycad level; therefore they are too much advanced to 

 throw light on the origin of a seed, and the question of the origin of 

 gymnosperms remains practically as it was before the discovery 



