Vegetable Morphology. 39 



perform has influenced many. He distinguished two 

 factors in development: (i) the law of growth, which 

 depends upon the inherited potentialities of the germinal 

 material; and (2) the conditions of development, such 

 as amount and distribution of yolk, pressure of mem- 

 branes, and surrounding medium. In terms of these 

 he sought to explain the foldings, the ingrowths, the 

 outgrowths, and other processes in development. Prof. 

 A. Rauber developed similar ideas in his Formbildung 

 und Formstorungy and it is interesting to notice how 

 this anatomist has of recent years made a specialty of 

 crystallization. Prof. Sachs, on the botanical side, was 

 also keenly interested from an early date in the 

 problems of causal morphology. 



The fresh movement has not, as yet, led to the solu- 

 tion of any big problem, but it has been attended with 

 much detailed success. Hertwig and Driesch, Herbst 

 and Dreyer, Wilson and Loeb, have been prominent 

 among the many workers. The gist of their method is 

 by artificial Formstorung to get hold of clues which may 

 aid in the understanding of normal Formbildung ; and 

 although there is much disagreement naturally inci- 

 dent on a new departure the work of the experimental 

 school has impressed biologists with the hopefulness of 

 looking for the immediate stimuli and essential condi- 

 tions which determine each successive expression of the 

 potentialities of the germ-plasm. 



Chapter V. 

 Study of Structure (Vegetable Morphology). 



Early Anticipations Metamorphosis in Flowering Plants Wolff 

 Goethe Subsequent Development Foundations of Exact Morphol- 

 ogy Comparative Embryology Alternation of Generations Study 

 of Alga, Fungi, and Lichens. 



Although it is possible to find in the works of Aristotle 

 and Theophrastus, and other ancient authorities, in- 



