PRESIDENTIAL ADDRESS. 557 



ovules of Juglans regia, and in a few allied genera, such as Morus and Urtica. 

 Also in a large number of Amentales with anatropous ovules (Quercus, Corylus, 

 Oastanea, &c), Miss Kershaw has demonstrated the occurrence of a w. ell- 

 developed integumentary vascular supply. No doubt a further search may re- 

 veal the occurrence of this feature in some other dicotyledonous ovules, but in 

 the meantime it seems difficult to believe that such a primitive vascular system, 

 which the Amentales share with the older Gymnosperms, would have been re- 

 tained in the catkin-bearing group, if it had undergone far-reaching floral dif- 

 ferentiation, while it had disappeared from the plants which in other respects 

 remained primitive. It would be still more difficult to imagine that it had 

 arisen in the Amentales subsequently to their specialisation. 



There are other structural characters and general morphological considera- 

 tions, which I have not time to deal with, which underlie the belief in the 

 primitiveness of the Amentales and some allied cohorts, and I trust they will 

 be set forth in detail by a better systematist than I can claim to be. My object 

 in bringing the matter forward at all is to point out some of the difficulties 

 which prevent me from accepting a monophyletic origin of the Dicotyledons 

 through the Ranalian plexus. 



One of these difficulties lies in the relationship of the Gnetales to the Dico- 

 tyledons. Arber and Parkin have recently made the attempt to gain a clearer 

 insight into the affinities of this somewhat puzzling group by applying to it the 

 ' strobihis theory 6 of Aiigiospermous descent.' The peculiar structure of the 

 flowers of Welwitschia lends itself particularly well to a comparison with those 

 of Cycadoidea, and a good case can no doubt be made out for a hemiangio- 

 spermous ancestry of this member of the Gnetacese, and by reduction the other 

 members, in many respects simpler, might be derived from a similar ancestor, 

 though probably, as far as Ephedra and Gnetum are concerned, an equally good, 

 if not better, comparison, might be made with Cordaites. But even supposing 

 we admit the possibility of a derivation of the Gnetales from an amphi- 

 sporangiate Pteridosperm, I think the Amentales merit quite as much as the 

 Gnetales to be considered as having taken their origin separately from the 

 Hemiangiospermae, and not from the Ranalian plexus. I find this view has 

 been put forward also by Lignier T in his attempt to reconstruct the phylogenetic 

 history of the Angiosperms, and I feel strongly that such a polyphyletic 

 descent, whether from the more specialised anthostrobilate Pteridospermse or 

 from several groups of a more primitive Cycado-Cordaitean plexus, is more in 

 accordance with the early differentiation of the Cretaceous Angiosperms, and 

 with the essential differences existing now in the orders grouped together as 

 Archichlamydese. 



Attempts at reconstructing the phylogeny of the Angiosperms are bound to 

 be at the present time largely speculative, but we may possibly be on the 

 threshold of the discovery of more certain records of the past history of the 

 higher Spermaphyta, since Dr. Marie Stopes has commenced to publish her in- 

 vestigations of the cretaceous fossil plants collected in Japan, and Professor 

 Jeffrey has been fortunate enough to discover cretaceous plant-remains showing 

 structure in America. The former have already provided us with details of an 

 interesting Angiospermic flower, and if the latter have so far only yielded 

 Gymnosperms, we may at all events learn something of the primitive forms of 

 these plants, the origin of which is still as problematical as is that of the 

 Angiosperms. 



I trust that the criticisms I have made of the theory put forward by Messrs. 

 Arber and Parkin will not be taken as a want of appreciation on my part of 

 the service they have done in formulating a working hypothesis, but merely as 

 an expression of my desire to walk circumspectly in the very alluring paths 

 by which they have sought to explore the primaeval forest, and not to emulate 

 those rapid but hazardous flights which have become so fashionable of late. 



While the description of new and often intermediate forms of vegetation 



* Arber, E. A. N., and Parkin, J. :' Studies on the Evolution of Angiosperms,' 

 'The Relationship of the Angiosperms to the Gnetales,' Annals of Botany, 

 vol. xxii., 1908. 



' Lignier, O. : ' Essai sur l'Evolution morphologique du Regne vegetal,' Bull. 

 de la Soc. Linneenne de Normandie, 6 ser., 3 vol., 1909, reimprime fevrier 1911. 



