170 MORPHOLOGY OF SPERMATOPHYTES 



sperms and the Pteridophytes to one another, and does not con- 

 cern itself in any way with the Angiosperms. 



Assuming the origin of Gymnosperms from Pteridophytes 

 as true, the question is as to the monophyletic or polyphyletic 

 origin of the group. Was a single group of archaic Gymno- 

 sperms derived from Pteridophytes, which subsequently differ- 

 entiated into distinct lines; or have several Gymnosperm lines 

 originated independently from the Pteridophyte stock? The 

 great diversities which exist among the living representatives of 

 the group suggest a p^l^phyle^tic_^rigin^ but the numerous im- 

 portant structures in common, and more than all the testimony 

 of the great Gymnosperm plexus of the Paleozoic, seem to argue 

 far more strongly for a monophyletic origin. The reasons for 

 these views will become more clear as the interrelationships of 

 the groups are considered. 



Assuming the monophyletic origin of Gymnosperms, the 

 question is at once suggested as to the special group of Pterido- 

 phytes which gave rise to them. Curiously enough, each of the 

 three living phyla of Pteridophytes has been claimed as having 

 been the source of the Gymnosperms. The hypothesis which 

 looks to the Calamodendreae among the Equisetales as the an- 

 cestral forms has now few if any supporters. A persistent 

 hypothesis, however, associates Gymnosperms with the Lycopo- 

 diales, through such ancient forms as the Sigillarieae, an origin 

 whicH is claimed for the Coniferales, even when the Cycads are 

 acknowledged to be of filicinean origin. A third hypothesis 

 would derive the Gymnosperms from the Filicales. As Pro- 

 fessor Scott has said : * " These interpretations, whether right 

 or wrong in the particular cases, at least indicate the broad fact 

 that important anatomical characters, which \ve are accustomed 

 to associate with Gymnosperms and dicotyledonous Phanero- 

 gams, were in Paleozoic times common to a large proportion of 

 the vascular cryptogams. Community of secondary tissue for- 

 mation, however, is by itself no proof of affinity, and the problem 

 must be attacked on other lines." 



The view which we maintain is that the Cycadales have un- 

 doubtedly been derived from the Filicales, and that it is impos- 

 sible to dissociate the other Gymnosperm lines from the Cycads. 



* Studies in Fossil Botany, p. 513, 1900. 



