THE PHYSIOLOGICAL ASPECT OF A SPECIES 



DR. D. T. MACDOUGAL 



Thk simple recognition of ditto rent kinds of plants 

 must be of great antiquity, and perhaps no single idea 

 affords a better index of scientific thought during the 

 last few centuries than the species conception. The 

 occasion does not warrant a detailed statement of its de- 

 velopment farther back than the time of Linnaeus, who 

 gave the idea a distinctly morphological stamp which it 

 has retained to the present day. His systematization of 

 natural objects marked the beginning of a period in 

 which the morphological view of nature has prevailed 

 throughout, the mechanics of form reaching its very 

 apotheosis in the writing of De Candolle, De Bary, Hof- 

 meister, Schwendener and a score of other eminent in- 

 vestigators who have triangulated the Held of natural 

 history of plants, basing relationships and constructing 

 systems of phylogcny upon pure form, and upon the 

 mechanical relations of cell-structure. 



and endless evolutionary change took on definiteness and 

 clearness with the writings of Lamarck, and this has 

 grown until a distinctly vitalistic and genetic view-point 

 has been gained, with the inevitable rearrangement of 

 perspectives and modifications of conclusions as to the 

 groupings and manner, of relationships among living 

 things. 



Latterly, after statistical methods had reached a state 

 of fair efficiency, their introduction into the study of 

 occurrence, characters, distribution and form, has re- 

 sulted in leading consideration from the type or the indi- 

 vidual, to aggregates, or to the whole mass of individuals 



