No. 508] 



STUDY OF VASCULAR ANATOMY 



225 



upon establishing a phylogenetic connection between 

 Gnetales and angiosperms claim only that they are lines 

 of parallel development from a common hypothetical 

 ancestry. It is the use of history as a check that has 

 changed our point of view as to phylogeny more than any 

 single factor; and it is the recent vascular anatomy that 

 has given us a trustworthy history. 



The transformation in our conception of the inter-re- 

 lationships of pteridophytes deserves mention. Ever 

 since alternation of generations was recognized, the ordi- 

 nary fern, with its seductive prothallium, has been gen- 

 erally thought of as the living pteridophyte nearest the 

 bryophyte level. It is now recognized that the Filicales, 

 as a whole, are more clearly connected with seed-plants 

 than is any other group of pteridophytes, and that we 

 must look elsewhere for the most primitive living type of 

 vascular plants. Whether we find them in some of our 

 club-mosses or in Ophioglossum may be an open question 

 for some, which vascular anatomy and history are in a 

 fair way to decide. In any event, vascular anatomy and 

 history have strikingly confirmed, in a general way, the 

 conclusions of the morphology of reproductive parts. 



The change of view as to gymnosperms has perhaps 

 been the most striking change of the last decade, and this 

 has ,een brought about by remarkably aggressive work 

 in VI lines of approach, beginning with the discovery of 

 swi nming sperms in the cycads and Ginkgo. Of course, 

 the most sensational discoveries since have been the ex- 

 istence of Cyeadofilicales and the remarkable strobilus of 

 thj Bennettitales. These discoveries have been supple- 

 mented by morphological work in almost every genus, 

 anatomical work in all the important groups, and an un- 

 precedented uncovering of the gymnosperm history. Now 

 we recognize the group as starting with fern-like plants, 

 bearing microsporangia and megasporangia as the ferns 

 do sporangia. From this start a strobilus was worked 

 out, whether primitively monosporangiate or amphispo- 

 rangiate or both is not clear. One line (cycadophyte) 



