380 



SCIENCE. 



[N. S. Vol. VIII. No. 195. 



than in Cordaites — in fact, more reduced 

 than in most living cycads and conifers. 



Additional testimony to the same effect 

 is furnished by sections of the seeds of Cor- 

 daites. In addition to the remarkable nu- 

 cellus beak, which probably has no phy- 

 logenetic significance, the large pollen 

 chamber is a conspicuous feature. This is 

 sometimes so extraordinarily large that it 

 occupies the whole upper portion of the 

 nucellus, and has been observed to contain 

 numerous pollen grains. The pollen cham- 

 ber is a well-known cj^cad feature, and 

 seems to be associated with the early de- 

 velopment of siphonogamy. By means of 

 it, the tubular outgrowth from the anthe- 

 ridium wall is reduced to a minimum, and 

 may coexist with spermatozoid develop- 

 ment, as shown by Hirase, Ikeno and 

 Webber. 



The testimony all indicates that in Cor- 

 daites we have the beginnings of a sipho- 

 nogamic line, brought about by the reten- 

 tion of the megaspore, which still develops 

 its exine in Cordaites and some cycads. 



As to the ptei-idophyte group from which 

 the Cordaites were derived, data are not 

 sufficient to make opinion other than a pure 

 hypothesis. I think it is clear that such 

 heterosporous pteridophytes as are living 

 to-day must be set aside in this search, by 

 the testimony of both of their gameto- 

 phytes, especially the male. They stand 

 for lines which have very much reduced 

 the male gametophyte, have variously mod- 

 ified the female gametophyte, but have not 

 developed siphonogamy by retaining the 

 megaspore. It may be that the lycopod 

 forms of the Carboniferous and earlier for- 

 mations represent the pteridophyte plexus 

 from which Cordaites were derived, but we 

 know too little of their morphology to 

 make any assertion. My judgment is that 

 the Cordaites represent an independent 

 heterosporous line, and that if they were as- 

 sociated in origin with the lycopod forms at 



all it was before the latter had developed 

 heterospory, which seems never to have 

 been extensively developed in the lycopod 

 line until recent times. 



I believe that we must regard either the 

 ancient homosporous lycopod forms or the 

 abundant Palseozoic Marattia forms as re- 

 sponsible for the origin of Cordaites, and 

 my own inclination is toward their Marat- 

 tia origin, perhaps for no better reason than 

 that in such an origin I see more oppor- 

 tunity for the development of such a group 

 as cycads ; but such a view is further sup- 

 ported by the discovery that the spermato- 

 zoids of cycads, and their ally, the Ginkgo, 

 are of the multiciliate type, and not bicil- 

 iate, as in living lycopod forms. Just what 

 sti-ess should be laid upon this I do not 

 know, but when opinion is fairly balanced 

 it would seem to help to a decision. It 

 seems satisfactory, therefore, to regard the 

 origin of cycads as from the homosporous- 

 eusporangiate plexus of Filicales, repre- 

 sented to-day most abundantly by Marattia 

 and its allies. It would seem, further, that 

 this has been brought about without the in- 

 tervention of such Cordaites as we recog- 

 nize, which, with probably similar origin, 

 were developing a very different type of 

 body, which finds its modern expression in 

 the conifers. In the acknowledged Cor- 

 daites, therefore, I recognize a transition 

 region between the homosporous-eusporan- 

 giate plexus of Filicales and the more mod- 

 ern conifer series ; while in the cycads we 

 have a line which continued more of the 

 fern habit and structure, recognizable not 

 merely in its foliage leaves and general 

 port, but in its occasional vascular bundles 

 of concentric type and its multiciliate 

 spermatozoids. The Cordaites, however, 

 must have included forms that we have not 

 recognized as such, for it is only when they 

 become differentiated from the fern habit 

 that in the main we are able to distinguish 

 them. This very fact of their sharp differ- 



