105 
anything under appropriate conditions, and is not destined to be some 
particular structure. 
One of the most interesting recent results of experimental morphology 
has been that obtained in experimental work on heterospory. It has been 
shown that it is possible to develop megaspores from cells that ordinarily 
develop microspores. It is such results that are playing fast and loose 
with our old conceptions of rigidity of structure and function. 
I can merely mention the field of plant physiology. If I speak of the 
changes that have taken place within the last twenty-five years, IT must 
show the atmosphere. in which we are living by assuring you that I am 
not the one to make such a presentation. In the old days one man taught 
all there was of botany, and probably he taught all there was of science. 
Today I have been compelled to ask a competent plant physiologist con- 
cerning the notable changes. He tells me that there are two conspicuous 
changes in the point of view. One is the gradual passing of the old vital- 
istic idea, which implied that there was some such thing as vital force that 
explained most things. Now the facts are explained, not in terms of vital 
force, but in terms of chemistry and physics. Another shifting point of 
view is a change from the old iGea that form and structure are the result 
of some mysterious law of development, to the idea that form and struc- 
ture are entirely expressions of the conditions under which growth has 
been conducted. 
The very new field of ecology at present is in the condition of these 
other fields more than a decade ago. Young fields are largely jokes to the 
older ones; but there has been a change in ecology during the last few 
years. It has passed from the stage of inchoate observation, in which in- 
struction in ecology could not be differentiated with distinctness from 
holiday excursion, to methods of precision. 
In conclusion, as one looks out over this great progress, he finds that 
it is all really an inevitable evolution from the stimulus that was given 
first by Hofmeister in 1898 te morphology, and ten years later by Charles 
Darwin to biology in general. 
University of Chicago, 
Chicago, Ill. 
