478 ANDREWS: PROTOPLASMIC STREAMING IN Mucor 
more or less collapsed or their diameter somewhat reduced after 
the loss of a considerable quantity of water. Even when all 
streaming has ceased and collapse of the filaments has then oc- 
curred to a quite noticeable degree, they may recover their normal 
dimensions and streaming recommence if they are surrounded 
with moist air from which the water is reabsorbed by the filament. 
In one experiment, when this collapse occurred in 22 minutes in 
air dried by 50 per cent glycerin, recovery in saturated air took 
place in 52 minutes and streaming reoccurred. Collapse and 
cessation of streaming can easily be produced over 50 per cent 
glycerin solution in considerably less time than it is possible to 
restore the filaments fully to the normal condition. 
As was to be expected, when the solutions of glycerin employed 
were made weaker, the effect on streaming as the result of weaker 
transpiration was less pronounced. For example, when Mucor 
stolonifer and M. Mucedo were placed over a 20 per cent solution 
of glycerin the streaming stopped in one hour. During all this 
time the streaming was, as in the 50 per cent glycerin, to the tips 
exposed to the air that was being dried by the glycerin. The 
streaming was not so rapid as over the 50 per cent glycerin. 
After replacing the specimen in saturated air streaming recom- 
menced and regained its normal velocity much sooner than when 
left an equal time over 50 per cent glycerin. Frequently all that 
is necessary to produce streaming in such fungal filaments which 
apparently are inactive, is to cause transpiration by drying the air 
around them with glycerin and as a rule only slightly. The effects 
of still weaker solutions of glycerin will be seen by the following 
experiments. When the fungi were placed over a 10 per cent solu- 
tion of glycerin the transpiration was so diminished that streamims 
continued for 3 hours to the portions exposed. When they were 
placed over a 714 per cent solution slow streaming was to be see? 
to the transpiring parts for 5 hours. When they were placed 
over a 5 per cent solution of glycerin the streaming was stl 
visible 8 hours after the experiment was started, and the filaments 
were not perceptibly dried up. The transpiration was very slow 
and streaming was always to the exposed parts. 
In several of the experiments, where the spores were grown 
under the cover glass, bubbles of air of different sizes were also 
