806 



THE AMERICAN NATURALIST [Vol, XLT 



prothallium and embryo. The species in which the bisporangiate 

 cone is best shown has been named Cycadcoidca dakotemis. 



In chapter nine there is given an excellent comparison of the exist- 

 ing and fossil cycads. There are but one hundred and seven described 

 species of living cycads, included in nine genera, of which four belong 

 to the New World and five to the Old World (including Australia). 

 As we have seen in the consideration of Chamberlain's and Caldwell's 

 papers, three of the four American genera are of very limited flistribu- 

 tion, Zamia being the only American genus of fairly extended range. 

 Three of the Old World genera, /. c. (\cas, Encephalartos and Macro- 

 zamia, are much morc^ widc^spr<>ad. As is well known, the cycads 

 were a predominate ])lan1 u [h- .hiring nu.M of the Me.ozoic, uhen this 

 type reached its culmination. 



The affinities of the cycads with f(;rns lunc been long recognized 

 and Wieland's work .trongly confirms the xieu that thcM- liaxe arisen 

 from ferns of marattiaceous affinity. The e\t r.iordiiiaril^ Ahirattia- 

 like microsporangial sori of Cycadeoidea are especially strikuig in this 

 connection. Wieland discusses the question A\liether the Cycadeoi- 

 deae, that is, those forms with bisporangiate cones, should be separated 

 as a special order, Bennettitiales, as recognized, among other authori- 

 ties, by Engler and Prantl. This view is not accepted by all botanists 

 however, some of whom, like Scott, recognize three families, Cycadeae,, 

 Zamieae and Bennittiteae, all referable to a single order, Cycadales. 

 This latter \icw is supported by Wieland, ^^ho beliexes that from the 

 great complex of Cycadofiliees or rt(;ridosj)erms (seed-bearing ferns) 

 a group which is now known to have been liighly develo[)ed during 

 the Paleozoic, there arose the common ancestors of the true cycads 

 and Bennittiteae, the group becoming more and more divergent as 

 they developed tlirough the lAIesozoic. Of these two divisions, only 

 the true cvcads have survived to the present time. 



The final chapter is taken up with a discussion of the relation of the 

 CAca<i> to the ferns and of tlie analogies exhibited between the floNver 

 of the Cvcadeoideae and those of the angiosperm.. The strong 

 e%idence that the (\cadale> are <h>M onded more or le.s directly from 

 marattiaceous ancestors is sunn.iarized. and after pointing out the 

 numerous points of res(Mnblance the author .says: " Plainly the 



groii|)s MS (•(,tnbin(Ml and showing their descent from marattiaceous 

 ferns of the Paleozoic is not merely conclusive, but one of the great 

 cornerstones upon which the plan of evolution can rest secure." 



It is evident that having to deal with such an enormously compli- 



