204 Macfarlanc — Current Problems in Plant Cytology. 



debated, the necessity for some critical standard of reckoning 

 has doubtless been painfully felt. The possible transmission 

 of characters has been debated, but the vaguest views have 

 been expressed as to what such characters are. Or again, 

 species have been described as new which differed only from 

 some older type in the size or folding of some part, in its 

 relative hairiness, in its prostrate or upright habit, or in certain 

 color effects. 



One great occupation in the coming century will undoubt- 

 edly be, the elucidation of the precise morphological details 

 of varieties and species, as being the only correct guide to the 

 evolutionary affinities of our plant groups, and the segregation 

 of species within these. All this must be accomplished from the 

 standpoint of the cell as the ultimate factor. Whether in the 

 upbuilding of unicellular or multicellular hairs of definite 

 structure, in the presence of definite pigments over certain 

 areas, in the development of thickening zones and other 

 structural features, precise information is only obtained when 

 such are recorded in terms of cell life. It will then be possi- 

 ble to classify plants on a natural plan, instead of as now by 

 selecting one or two points of resemblance — not necessarily 

 of morphological contact — as a taxonomic basis. 



When such data shall have accumulated, the student of 

 plant evolution will be in a position to compare varieties and 

 species morphologically, to inquire intelligently how these are 

 related to their environment, and to determine the limits 

 within which variation may take place in a given time or under 

 given conditions. The small beginnings have already been 

 made, the coming century will doubtless witness the great 

 continuations. Problems of surpassing interest invite our 

 attention. My earnest hope is that our Society shall aid in 

 the solution of some of them, and that annual contributions 

 of ever-increasing value will be made to its Proceedings. 



