700 
Fritsch and Haines .— The Moisture-relations 
D. The Effect of Prolonged Action of the Plasmolysing 
Solution. 
In a considerable number of cases material, with the edge of the cover- 
glass sealed as described above (p. 689), was estimated at daily intervals ; 
between the successive determinations the slide was usually exposed to 
room temperature and to a moderate illumination. Some of the results are 
epitomized in Table IX (cf. also Fig. 7). It will be seen that in the 
filamentous forms there is invariably a recovery from plasmolysis, analogous 
to but not always as marked as the final response on the part of drought 
material to plasmolysing solutions. In both cases there is a very appreciable 
reduction in the number of strongly plasmolysed cells, and the usual increase 
in the number of slightly plasmolysed cells in the final stage is here, too, no 
doubt due to the fact that a larger or smaller number of the cells have their 
protoplasts in a permanently contracted condition (cf. pp. 691,716) ; that this 
was the case could naturally only be established at the end of each experi¬ 
ment. The moss protonema again stands out more strikingly in this respect 
than do the filamentous algae. Attention may be drawn to the fact that 
a larger percentage of dead cells was invariably found at the end of the 
experiment in the filamentous forms. Whilst we do not attach much impor¬ 
tance to the estimations of dead cells, since the liability to error is much 
greater here, the results are so uniform that they can scarcely be due to 
chance. 
With the unicellular forms the results are almost as difficult to under¬ 
stand as in the case of the drought experiments considered in the preceding 
section. Thus, whilst in Experiments VII and XXVIII with Pleurococcus an 
obvious recovery was noted, Experiment XVII and others no tincluded in 
Table IX showed no alteration in the material that could be regarded as 
beyond the limits of experimental error, a similar conclusion being reached 
in the case of Cystococcus. In Experiment XXVIII there was no appreciable 
recovery during the first four days, but after that a rapid change took place, 
so that on the eighth day practically no plasmolysed cells were to be found. 
It thus appears that Pleuroccccus is usually capable of remaining unaffected 
by the unfavourable conditions in a sealed slide for a much longer time 
than the filamentous forms, in which the recovery is very rapid (cf. below), 
and the duration of its resistance may well depend on the condition of the 
original material. This would explain the discrepancy between the different 
experiments. In this connexion attention may be drawn to the fact that in 
Experiment XVII, in which no recovery was noted, there is no difference 
between the percentages of dead cells at the beginning and end of the experi¬ 
ment, implying considerable power of resistance on the part of the material. 
In Experiment XXVIII, on the other hand, there were far more dead cells at 
the end of the experiment than at the outset. 
