720 
Fritsch and Haines. 
The Moist it re-relations 
(d) Investigation of Centrifugalized Material. 
As a further method of investigating the supposed change in viscosity 
of the protoplasts (cf. above), the effect of centrifugalizing at a speed of 
2,500 revolutions per minute on the position of bodies within the cells was 
examined. If fresh material of Spirogyra, Zygogonium , Hormidium , or 
moss protonema, placed together with a little water in the bottom of the cen¬ 
trifuge tube, be subjected to the centrifugal force mentioned for 15 minutes, 
a pronounced displacement of nucleus and chloroplasts to the side of the 
cell takes place. In the case of the two terrestrial algae the granules ‘ cream ’ 
in the opposite direction to the chloroplast, thus affording additional evidence 
of their fatty nature. On the other hand, in Pleurococcus and Prasiola no 
displacement of the cell-contents was to be observed, even after one hour’s 
centrifugalizing at the above speed. 
A similar test was applied to material of Zygogonium , Hormidium , and 
moss protonema, which had been exposed to four days’ drought over 34*5 
per cent, sulphuric acid in the dark at 18 0 C. Before centrifugalizing, the 
material was thoroughly soaked and was then placed in water in the centri¬ 
fuge tube. In this case neither one-quarter hour nor one hour’s centrifugaliz¬ 
ing served to bring about any alteration in the cell-contents, which appeared 
in the same position as in uncentrifugalized material. The mats were then 
thoroughly soaked arid some of the material subjected to the same treat¬ 
ment three days later, but no difference as compared with the drought 
material was to be noticed. It should be added that, at the time when the 
drought material was centrifugalized, parts of the same mats which had been 
kept moist in the thermostat urider otherwise similar conditions to those to 
which the drought material was exposed were also centrifugalized, and after 
a quarter of an hour showed the same kind of displacement as the original 
material. This proved that the features observed in the drought material 
are not a result of exposure to the conditions extant in the laboratory. 
The observations made on centrifugalized material thus afford a striking 
confirmation of the view, derived from the examination with dark-ground 
illumination, that as a result of drought there is a great increase in the 
viscosity of the protoplasm in Zygogonium , Hormidium , and the moss 
protonema. In Pleurococcus and Prasiola , on the other hand, such high 
viscosity of the protoplasm is evidently the normal condition. This feature 
accounts for the inert character of drought material and, in the case of the 
two forms last mentioned, even of the fresh condition. 
The effects of centrifugalizing on material which had been immersed for 
some time in sea-salt solutions was only tried on Zygogonium two days 
after Experiment XXXV had been in progress. After a quarter of an 
hour’s centrifugalizing most of the cells did not show any displacement, 
but in a few cases it was quite marked. 
