May 31, 1907] 



SCIENCE 



859 



of Gycadeoidea and Bennettites gibsonianus, 

 or allied species, far the larger portion were 

 actually bisporangiate and discophorous. That 

 this conclusion has not resulted from previous 

 studies, and that it has only rarely been sug- 

 gested in a modified form, is ascribed to the 

 imperfection of the longitudinal sections of 

 cones. 



The orthotropous seeds are about the size 

 of a small grain of rye, and each is produced 

 on a separate pedicel. Only one coat encloses 

 the nucellus. In this respect Gycadeoidea 

 wielandi is comparable with Bennettites mori- 

 erei from which, however, it differs in detail 

 to such an extent that the two can not be 

 homologized with certainty. The seed coat of 

 the former is nevertheless exactly comparable 

 with Lagenostoma, which, of all the existing 

 and extinct forms thus far discussed, affords 

 the most striking structural parallels with 

 American Cycadeoidea seeds. 



A further parallelism between the American 

 Gycadeoidea dacotense and 0. wielandi, and 

 the European Bennettites gihsonianus and B. 

 morierei, is to be found in the presence of well- 

 marked dicotyledonous embryos which more 

 or less nearly fill the entire space and indicate 

 a nearly, if not complete, exalbuminous condi- 

 tion. These embryos are strikingly like those 

 of GingJco. Evidence has also been obtained 

 with respect to the existence of an earlier 

 or preembryonic stage which has never been 

 found preserved in any other specimen or 

 hitherto observed in any other fossil gymno- 

 sperm or other plant. The evidence points to 

 the replacement of the oospore by a homo- 

 geneous tissue and the absence of a suspensor. 

 The embryo was therefore formed directly 

 through growth of the oospore which thus 

 represents the proembryo or protocorm. The 

 suggestion arising from these facts is an 

 analogy with Ginlcgo in which there is a much 

 more simple form of embryogeny than in other 

 gymnosperms. 



One of the most striking facts revealed by 

 the studies so far completed, is that the hiatus 

 between the two great Cycadean lines is of a 

 two-fold character. In existing cycads great 

 complication of the cortical bundle system has 

 developed, while the reproductive organs are 



relatively little changed and primitive. Con- 

 versely, in the Cycadeoidese there is a retention 

 of the primitive cortical system together with 

 the most surprising reproductive changes lead- 

 ing up to the bisexual flower which mimica 

 that of the angiosperms. It is therefore 

 natural to ask if two groups so related shall 

 be included in one greater class, the Cycadales, 

 or the Cycadeoidese be excluded from the true 

 Cycadales, as Bennettitales or Cycadeoidales ? 

 After a careful review of the positions taken 

 by Scott, Zeiller, Potonie and Count Solms, 

 and of the evidence afforded by the paleon- 

 tological record, it is held that the Cyca- 

 deoidesB find their appropriate place amongst 

 the true Cycadales. 



An. interesting summary of the fern-cycad 

 relations, together with suggestions bearing 

 upon analogies of the ferns and angiosperms, 

 closes a very able treatment of a difficult but 

 intensely fascinating problem. The general 

 tendency of the evidence is to greatly 

 strengthen the current views respecting the 

 marattiaceous origin of the cycads; or, in the 

 pregnant words of the author " The preceding 

 resume of the principal characters of the two 

 great cycad groups as combined and showing 

 their descent from marattiaceous ferns of the 

 Paleozoic, is not merely conclusive, but one of 

 the great cornerstones upon which the concep- 

 tion of evolution can rest secure." 



D. P. Penhallow 



MONTEEAX, 



May, 1907 



SCIENTIFIC JOURNALS AND ARTICLES 



The April number (voluipe 8, number 2) 

 of the Transactions of the American Mathe- 

 matical Society contains the following papers : 



E. Kasnee: 'Bynamical trajectories: the mo- 

 tion of a particle in an arbitrary field of force.' 



W. R. LoNQLET: 'A class of periodic orbits of 

 an infinitesimal body subject to the attraction of 

 n finite bodies.' 



E. B. Van Vleck: 'A proof of some theorems 

 on pointwise discontinuous functions.' 



L. E. Dickson : ' Invariants of binary forma 

 under modular transformations.' 



E. J. WiLCZTNSKi: 'Projective diflferential 

 geometry of curved surfaces ( First memoir) .' 



J. I. Hutchinson : ' A method for constructing 



