DEVELOPMENT OF MORPHOLOGICAL CONCEPTIONS 11 



who has passed through all the phases of morphology described 

 above, that the conception of species has become so radically changed 

 that a reconstructed taxonomy is inevitable. When the doctrine of 

 types disappeared, and when experimental morphology showed the 

 immense possibilities of fluctuation in taxonomic characters, the 

 taxonomy of the past was swept from its moorings. Taxonomy 

 must continue its work as a cataloguer of material, but to catalogue 

 rigid concepts is very different from cataloguing fluctuating varia- 

 tions. To do the latter on the old basis is being attempted in 

 certain quarters, but it soon passes the limit of usefulness and sets 

 strongly towards the mere recording of individuals. Some new 

 basis must be devised, and it must be a natural and useful expres- 

 sion of the relationships of forms as suggested by experimental 

 morphology. 



That this history of the progress of morphology, just outlined, is 

 a fair indication of general tendencies may be illustrated from plant 

 anatomy. This subject, not well differentiated from plant mor- 

 phology among the lower groups, has developed a very distinct 

 field of its own among vascular plants. Its early phase was that of 

 classification, in which types of tissues were rigidly defined. This 

 definite catalogue of tissues continued to be used after evolution- 

 ary morphology was well under way, and morphologists gradually 

 abandoned any serious consideration of it, just as they had cut 

 loose from the old taxonomy. In text-books the juxtaposition of 

 morphology upon an evolutionary basis and a little anatomy upon 

 a strictly taxonomic and artificial basis became very familiar. 



Recently a second phase of anatomy has begun to appear, and 

 we find it upon an evolutionary basis. Investigation has passed from 

 the study of mature tissues to the study of developing tissues, and 

 the seedling is more important to the anatomist than the adult 

 body. As in the corresponding phase of morphology, the funda- 

 mental conception of this new phase is the theory of recapitulation, 

 and its ultimate purpose is phylogeny. It views tissues as mor- 

 phology views organs, and is attacking the same general problems. 

 In so doing it becomes a special field of morphology, no more to be 

 separated from it than are morphologists who study the sporophyte 

 to be separated from those who study the gametophyte. It is simply 

 the development of another line of attack upon morphological prob- 

 lems. This anatomical morphology, as it may be called, has yet to 

 accumulate its share of results, and there is no region of morphology 

 more in present need of investigators. From the small beginnings 

 it has made it is evident that it must check the conclusions of the 

 older morphology at every point. Even now no statement as to 

 phylogeny can afford to neglect the testimony of anatomy. 



This second phase of anatomy promises to be accompanied by a 



