618 



SCIENCE. 



[N. S. Vol. XX. No. 515. 



In the second place, to outline the prog- 

 ress of biology even from the standpoint of 

 botany is too large a subject to be included 

 in the grasp of any one man in such a 

 way that he can recognize the movements 

 in his own experience. The general botan- 

 ist no longer exists except in name, and 

 any general survey of botanical activity 

 would have to be a compilation rather than 

 a contribution. With these limitations, it 

 beqomes necessary for me to restrict myself 

 largely to such an outlook as is given by 

 plant morphology, and even then to speak 

 only of those conclusions that come natu- 

 rally to one in contact with the morphology 

 of vascular plants. And yet I believe that 

 a history of the development of the funda- 

 mental conceptions of plant morphology 

 may be taken as a fair illustration of what 

 has been going on not only in botany in 

 general, but also in biology. 



In the third place, the period included 

 in this survey of plant morphology need 

 not extend beyond the middle of the last 

 century, for at least three reasons: (1) 

 The earlier progress of the science has been 

 outlined by Sachs in his admirable 'His- 

 tory of Botany'; (2) modern morphology 

 finds its beginnings in a very real sense in 

 the work of Hofmeister; and (3) Darwin's 

 theory of natural selection gave the strong 

 evolutionary impulse that it has felt ever 

 since. 



My principal theme, therefore, is the de- 

 velopment of morphological conceptions, as 

 illustrated by plant morphology. 



It would be confusing to introduce the 

 mass of details and the names of investiga- 

 tors suggested by this subject. Nor would 

 there be any advantage in recording the 

 changes of conceptions in reference to the 

 great variety of structures developed by 

 the plant body and in reference to their re- 

 lation to one another. My purpose is to il- 

 lustrate the general change of attitude, the 

 shifting of the point of view in reference to 



plant organs as knowledge has increased. 

 No definite names or dates can be cited, 

 for the movement has been general and 

 gradual, developed out of common expe- 

 rience and proceeding from the background 

 of accumulated knowledge. Disregarding 

 the numerous possible subdivisions, the 

 attitude of mind towards a plant organ 

 during the last half century has presented 

 three distinct phases. 



1 . THE PHASE OF THE MATURE ORGAN. 



At the beginning of the period undei: 

 consideration, the morphologist concerned 

 himself chiefly with completed organs, and 

 an overshadowing rigid taxonomy com- 

 pelled the idea of their classification. A 

 few theoretical types of organs had been 

 selected, and all organs were forced by the 

 doctrine of metamorphosis to lie upon this 

 Procrustean bed. All parts of vascular 

 plants, for example, were regarded as roots, 

 stems or leaves under various disguises. 

 It does not seem unreasonable to charac- 

 terize this conception as the arbitrary se- 

 lection of an ideal type, the natural off- 

 spring of the conception of ideal types that 

 prevailed in taxonomy. In other words, 

 morphology was dominated by taxonomy, 

 and morphologists were first and chiefly 

 taxonomists. It is this phase of morphol- 

 ogy that must continue to be exploited 

 chiefly by taxonomists, and which still re- 

 mains in those conservative schools in 

 which instruction lags far behind research. 

 This doctrine of types resulted in the cata- 

 loguing of organs just as species were being 

 catalogued, and, although capable of re- 

 cording material, was incapable of advan- 

 cing knowledge. 



An accompaniment of this mental atti- 

 tude was the explanation of metamor- 

 phoses. It is almost impossible for one age 

 to conceive of the mental condition that 

 was satisfied with the explanations of a pre- 

 vious age. In this case it must be remem- 



