707 
of Terrestrial Algae. II. 
tion of the majority; as a general rule the plasmolysis is not very extreme 
and its extent appears to undergo no appreciable alteration after the experi¬ 
ment has been in progress for some weeks. That these plasmolysed cells 
are otherwise perfectly healthy is shown by their capacity for immediate 
and complete recovery, even after weeks in the salt solution, when placed in 
tap-water. It should be especially emphasized that cells with uncontracted 
though quite healthy protoplasts were always to be found in the threads, 
even after many weeks’ sojourn in the salt solution, and this again implies 
on the part of a larger or smaller number of the cells a marked capacity for 
resistance to the high concentration of the surrounding fluid. Such cells 
may obviously be the starting-points for growth, and that this has only been 
observed in one instance may well be due to other conditions of the experi¬ 
ment being unsuitable. We hope to return to this problem at a later stage. 
The observations just detailed indicate that material permanently 
immersed in hypertonic solutions shows a failure on the part of many of 
the initially plasmolysed cells to recover. This conclusion is obviously at 
variance with the results obtained in the case of algal threads kept in 
a sealed slide which were considered in the earlier part of this section. It 
is for this reason that we regard these results as probably in part due to 
pathological causes. There is no doubt, however, that even in open solutions 
a gradual recovery takes place during the first days (cf. Table XII), but the 
recovery is probably again in great part pathological and followed by the 
death of the cells in question. Thus, whilst in the first days there is 
Table XII. 
Successive estimations of material of Zygogonium immersed in 5 per cent. 
sea-salt solution (Experiment XXXV). 
Date. 
Feb. 5 
» 6 
„ 7 
»> 9 
Cells 
Strongly 
Slightly 
Unaffected. 
0/ 
counted. 
plasmolysed. 
O/ 
plasmolysed. 
0, 
L 544 
Zo 
66-8 
Vo 
16-7 
Zo 
16-5 
1,021 
22*9 
23-4 
53*7 
1,000 
27-2 
10-7 
62*1 
1,030 
47*3 
21*8 
30-9 
a very obvious decrease in the numbers of plasmolysed cells, the per¬ 
centages of such cells tend subsequently to increase again in the direction 
of a maximum. This increase is, however, a deception and due to the fact 
that there is a great mortality among the unaffected cells, the plasmolysed 
ones which constitute the main mass of the healthy cells thus, although 
actually remaining constant in number, appearing to undergo a great relative 
increase. Whilst the majority of the healthy surviving cells are often 
plasmolysed, there are, as already mentioned above, always a number of 
healthy unaffected cells. It is probable that these are cells which were 
