MORPHOLOGY AS A FACTOR IN DETERMINING RELATIONSHIPS II 5 
herbaria and garden. It is my belief that this can be done best 
through a co-operation of the larger botanical institutions. It is 
manifestly impossible for any one institution to cover the whole field 
with any degree of satisfaction, but it is possible for each institution 
either to direct its energies to a particular territory or to a particular 
group of plants. Thus it would be possible to place in the hands of the 
research student an abundance of the necessary kind of material for 
comparative morphological study and afford the opportunity to de- 
termine the range of variability. 
Our conception of the origin and limitation of species has been so 
modified by recent investigations in plant breeding, mutation, hy- 
bridization, etc., that relationship in a line of evolutionary sequence is 
an extremely complex problem. Nevertheless the new morphology, 
the intensive study of cell-phenomena, and experimental work have 
done much to advance our knowledge of the relationship of organisms ; 
and it is not improbable that within a comparatively short time we 
shall have a more complete and satisfactory knowledge of the main 
phases of phylogeny and the chief lines of evolution of our higher 
plants. 
Missouri Botanical Garden, St. Louis 
