RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 569 
creature of its environment in the sense that the potentiaHties of the 
species may be called forth in greater or less degree, or the expression 
of them may be retarded by the conditions under which it grows. 
The effect produced may be due to the environment as a whole or to 
certain factors. Klebs and others have already proved that conditions 
determine what phase of the plant's growth shall appear and it has 
been shown in the preceding pages that these phases may be influenced 
by the conditions prevailing during vegetative growth. The plant 
therefore not only responds to the immediate environment but is 
molded by it in ways that can find expression only after that environ- 
ment has been changed for another. 
While growing vegetatively a mycelium may acquire a tendency 
toward the development of sporangia and oogonia and such a tendency 
may be carried over to the new environment into which the mycelium 
is transferred. This fact was recognized by Klebs who said ('99, 
p. 585) that in all investigations on the production of sporangia the 
nutrition conditions of the mycelium have a specific importance as 
upon them depends the ability of the mycelium to respond to the 
change in nutrition by the formation of reproductive organs. Klebs 
further states that these two forms of reproduction make different 
demands on the protoplasm (Nahrplasma), both quantitative and 
qualitative. So far as the present studies show, the minimum con- 
centration of peptone needed to grow a mycelium that will develop 
sporangia or oogonia is about the same, but the addition of sugars 
favored the production of oogonia and that of salts the production of 
sporangia. In this connection reference may be made to some 
observations not given in the data above. Mycelium of Achlya 
prolifera grown in solutions of peptone and potassium nitrate, when 
transferred to water developed sporangia more freely than that from 
any other solution and the sporangia were strikingly large, with dark 
walls. A similar observation was made on Dictyuchus monosporus, 
mycelium of which from solutions with potassium nitrate developed 
large dark sporangia, while that out of solutions with mono-potassium 
phosphate formed small light colored sporangia. This phenomenon 
was observed a number of times and proved quite constant and char- 
acteristic. 
The view that the fungus may, during vegetative growth, acquire 
a tendency toward the development of oogonia irrespective of the 
vigor of growth is strongly supported by the results obtained with 
