of Terrestrial Algae. II. 
703 
Table X. 
Estimation at half-hour intervals of percentages of plasmolysed 
cells of Pleurococcus (Experiment VII). 
Strength 
Cells 
Percentage 
plasmolysed. 
of sol. 
V 
counted. 
1st half-hour. 
2nd half-hour. 
/o 
15-0 
5°°, 5°2 
20-8 
19.1 
17*5 
5° 2 ? 5°5 
24.7 
20-4 
20-0 
502, 502 
30-5 
23-3 
22-S 
C/i 
O 
tsi 
O* 
O 
M 
37-3 
29.9 
2^-0 
5°i, 401 
48.7 
44-4 
In another case (Experiment XXIV) estimations of 1,000 cells were made 
at two-hourly intervals on a sealed slide with Pleurococcus kept in a warm 
room. There were some indications here of a daily cycle, the percentage 
of plasmolysed cells sinking towards midday and rising again in the evening 
and, during the two days of the experiment, showing a slight downward 
tendency. The results are not at all conclusive, but owing to the large 
amount of time consumed in such experiments it has not been possible to 
repeat them up to the present. 
Recovery from plasmolysis was also established in a very large number 
of cases by direct microscopic observation of small groups of initially plas¬ 
molysed cells over a period of several days. In the case of Zygogonium 
such recovery was repeatedly noted in 3, 5, and io per cent, solutions, being 
complete in about three days ; the recovery of granular cells was almost 
invariable, that of non-granular cells not so frequent, especially in the 
stronger solutions. Hormidium showed frequent complete recovery both in 
5 and 10 per cent, solutions. Moss protonema usually fails to recover, but 
in one set of cells complete recovery was observed in a 5 per cent, solution, 
never in a 10 per cent, solution; in most cases the extent of plasmolysis 
was found to increase at first and then to decrease again, although, as just 
mentioned, this only led to complete recovery in one thread. Analogous 
observations were also carried out on the cells of the leaves of a moss 
(Hypnum cupressiforme, L., var. filiforme , Brid.) and gave results quite 
identical with those just recorded for the protomena, recovery being only 
noted in one case in a 5 per cent, solution. In a few cases cells of a narrow 
species of Spirogyra showed recovery both in 5 and 10 per cent, solutions; 
more usually, however, they gave a negative result (cf. also Table XI); cells 
of Cladophora and Chaetophora in a 3 per cent, solution showed no decrease 
in shrinkage of the protoplasts during a period of ten days. The epidermal 
cells of Saxifraga sarmentosa lastly, though occasionally recovering in 
3 per cent, solutions, failed to show any recovery either in 5 or 10 per cent. 
3 A 
