570 
ADRIAN J. PIETERS 
levulose as a food as well as by those with phosphates. The fact that 
the effect of both levulose and phosphates was different on Achlya 
prolifera, from what it was on Saprolegnia serves to support this view 
and to show that the specific characters of different plants will react 
differently to similar environmental conditions. The close relation- 
ship existing between S. ferax and 5. monoica made it reasonable to 
expect that similar responses would be made by these species to like 
conditions. But Achlya is, in habit and in choice of habitat, very 
different. As Petersen ('lo) has pointed out, the Achlyas, though 
growing on dead animal matter, are frequently found on decaying 
plant parts, habitats not affected by the Saprolegnias. 
It seems probable that the specific response of the plants grown 
in levulose and in phosphates may be due to a storage of reserve 
materials which are drawn upon as soon as the fungus finds itself in a 
poorer nutrient medium. Klebs suggests this but seems also to hint 
at a more intimate change in the character of the plasma. It is 
sufficient for the present purpose to point out the fact that the specific 
effect of one solution may be to awaken an appropriate reaction when 
the mycelium is transferred to another solution. 
The Value of Levulose 
The results of the experiments on both Saprolegnia ferax and 
5. monoica support the statement that levulose is used more readily 
by these species than othei sugars except maltose and that it has a 
much greater effect in developing a tendency toward the production 
of oogonia than maltose has. This effect on the vegetating mycelium 
is confirmed in the case of both maltose and levulose by the effect of 
dilute solutions into which mycelia are transferred for the production 
of oogonia. In this case also maltose promotes vegetative growth to 
the almost entire exclusion of oogonia while levulose encourages the 
production of both oogonia and antheridia. The remarkable effect 
of levulose on some species was shown in the case of a still unde- 
scribed form which was collected as number 74. The details of the 
experiments with this form will be given in another paper but here it 
may be said that while, during almost two years of cultivation on 
natural and synthetic media, no oogonia were produced, these ap- 
peared when a mixture of leucin and levulose was used. The result 
was undoubtedly due to the levulose, as leucin alone or with any 
other carbohydrate or with salts failed to produce a like effect. 
