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of paleontology, but more vividly than in any other way by the 

 actual behavior of certain plants in the matter of giving rise to 

 new forms. This last consideration is of such great importance 

 that we shall come back to it later. 



One type of morphological investigation has to do with the 

 study of life histories of plants — the whole life story from egg 

 to egg again — and here we find the morphologist in close 

 relation with the systematist, for upon the results of such 

 researches must largely depend the understanding of the rela- 

 tionships of the great groups. The morphologist who devotes 

 his time to the study of life histories is engaged in the work of 

 tracing the race history of plants from the comparison of the 

 individual development of more or less nearly related forms. 

 Thus the homologies which have been traced among the flower- 

 ing plants and their nearest allies among the ferns and other 

 forms indicate to us the probable race history of these groups. 

 It is true that the beginning of this work dates back some 

 decades, but it is still, to a large extent, an open field, and numer- 

 ous investigators are actively prosecuting research along these 

 lines. For example, the alternation of a sexual and non-sexual 

 generation of plants which has long been known as characteristic 

 of the life histories of higher forms has recently been established 

 among the lower groups, and thus a much clearer view of the 

 whole series of the plant kingdom is being obtained. 



Somewhat separated, and to a large extent needlessly so, is 

 the work of the plant anatomist and histologist. Formerly pur- 

 sued from the standpoint of the mere topographical relation of 

 the parts, the conception of the plant as an organism with inter- 

 related and interdependent tissues began to fall into abeyance, 

 until a new point of view has within recent times revivified a 

 somewhat barren field. This point of view is the physiological 

 one, the correlation of structure and function. Here the student 

 of gross morphology and the anatomist unite in a physiological 

 interpretation of the form and structure of plant organs, from 

 which has grown the study of experimental morphology. 

 Advance in this direction has been considerable, and we have 

 now a much clearer idea of the nature and development of plant 



