No. 508] 



STUDY OF VASCULAR ANATOMY 



221 



anatomical rubbish pile, and it has been promptly and 

 warmly welcomed by modern morphology. 



The organization of vascular anatomy upon an evolu- 

 tionary basis came at a most auspicious time, for the 

 phylogenetic lines, guarded only by the anatomy of re- 

 productive structures, had begun to show signs of waver- 

 ing. Wider researches had begun to dissipate rigid 

 categories into mists. Such veterans of definition as 

 archesporium, sporangium, sporophyll, etc., had been put 

 to flight. Especially did experimental morphology play 

 havoc. It made hereditary structures lose their rigidity, 

 and raised the question whether the hen that sits on the 

 eggs is not more important than the one that lays them. 

 It certainly intensified the conviction that any structure 

 might arise any number of times. This made schemes 

 of phylogeny essentially paper schemes. They were 

 good illustrations of what the phylogenetic succession 

 might have been, but they could carry no assurance of 

 what the phylogenetic succession actually had been. 



This whole situation has been steadied, at least 

 morphologically, by the recent development of vascular 

 anatomy, including as it does the enormously important 

 ancient history of the vascular groups, which was largely 

 denied to the reproductive morphologist. The difference 

 between matching forms and investigating structure is 

 nowhere more clearly illustrated than in the recent de- 

 velopment of our knowledge of fossil plants. Morphol- 

 ogy, therefore, really has another ally that came in com- 

 pany with vascular anatomy, and that is actual history, 

 which must always be reckoned with. 



As a result of this triple alliance, what has been the 

 progress of morphology during the last decade? Our 

 subject necessarily limits us to the vascular plants; but 

 it might be said, in passing, that most important progress 

 has been made in bryophytes and thallophytes as well. 



Students of gametophytes and sexual organs, of spore- 

 producing members, of the vascular system, of fossil 

 plants, have been investigating with wonderful energy, 



