THE RELATION BETWEEN VEGETATIVE VIGOR AND 
REPRODUCTION IN SOME SAPROLEGNIACEAEi 
Adrian J. Pieters 
Historical Introduction 
Advances in science have been made by workers arriving at new 
points of view, as witness the work of Mendel, Darwin, deVries and 
others. So also the writings of Klebs during the last twenty-five 
years have served to open up a field, the cultivation of which is already 
exercising a profound influence on biological thought. Klebs was not 
the first to suggest that the forms, to the development of which a plant 
might at any one time devote its energies, were conditioned by ex- 
ternal factors acting upon the plant; but it will be neither necessary 
not desirable to review the older literature. This has been adequately 
done by Klebs in his various papers. (See especially 'oo, '03, '04.) 
The idea underlying all of Klebs's work is that every species has a 
sum total of potentialities constituting the specific nature of that 
species, but that the chemical and physical conditions prevailing at 
any one time within the organism determine which of the particular 
forms that the species is capable of producing shall appear, and that 
these inner conditions may be controlled, to an extent at least, by 
regulating the external conditions. In other words the changes 
in form which we witness in the course of the development of an 
individual are the results of chemical and physical interactions. 
Since 1890, when Klebs ('90) showed that the formation and 
discharge of zoospores in Hydrodictyon could be encouraged by 
providing certain conditions, he has established the truth of this 
principle in the case of other algae ('96), of fungi ('98, '99, '00), and 
also for flowering plants ('03, '04). Other workers have built upon 
1 Contribution 150 from the Botanical Department of the University of Michi- 
gan. This work was begun at Heidelberg, Germany, under the direction of Prof. 
Dr. Georg Klebs, and was continued at the University of Michigan under the direc- 
tion of Dr. C. H. Kauffman. To both of these inspiring instructors the writer wishes 
to return his thanks and to them he desires to express his appreciation of the mental 
stimulus he owes to their discussions and suggestions. 
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