697 
of Terrestrial Algae, II. 
75*4 per cent, slightly plasmolysed, and 5-2 per cent, unaffected cells. The 
air showed a very high relative humidity between the 20th and 27th, and 
this probably accounts for the result. Somewhat similar figures were 
obtained in an experiment with Zygogonium under the same conditions at 
the same time, and it was after these experiences that desiccation over 
sulphuric acid was substituted for mere drying in air. 
Table VII. 
Comparison of plasmolysis in material of terrestrial algae obtained from the 
same habitat on different occasions. 
Material. 
Zygogonium 
,, 
j> 
11 
U 
11 
Hormidium 
»» 
Jj 
Habitat. 
II 
»> 
III 
1 1 
II 
III 
11 
Date. 
Cells 
counted. 
Strength 
of sol. 
% 
Strongly 
plasmolysed. 
Slightly 
plasmolysed. 
Unaffected. 
0/ 
to 
0/ 
/o 
% 
I Feb. 
1 
2,008 
5 
12*5 
38-0 
49-2 
T A 9 O 
26 
1,987 
5 
69-9 
12*2 
17-9 
XVJ A & 
I Mar. 
20 
i,886 
5 
71 8 
21*7 
6*5 
1 Apr. 
1 
1,226 
5 
71-8 
16*8 
ii *4 
1923 
Feb. 
11 
4 
11 
L 544 
4,132 
5 
5 
66-8 
79'5 
167 
9*5 
16-5 
11*0 
1922 
Feb 
Mar. 
13 
1 
2,100 
2,053 
5 
5 
9 
62*1 
6-4 
33 -i 
i *9 
4*8 
T O') 1 ■ 
Mar 
27 
1,870 
5 
40-9 
4§*5 
io-6 
1923 
May 
1 
1,503 
5 
56-0 
39-0 
5 -o 
It is evident that an analogous alteration in behaviour towards plasmo- 
lysing solutions is to be observed also in a state of nature. In Table VII 
are given some data that bear on this point. The most striking feature 
about the four estimations of Zygogonium from habitat II is the astonishing 
uniformity of the last three. The first one, on Feb. 1, was made just after 
a dry spell, whilst the remaining three all fell within a period of intermittent 
wet weather. The two estimations of this alga from habitat III were like¬ 
wise made during a spell of wet weather. In the case of the Hormidium 
f from habitat II the first estimation was made after wet weather, the second 
after a few days’ lull. It is hoped in a later communication to produce more 
data with reference to the changes in terrestrial algae under varying con¬ 
ditions of humidity in nature, the data just offered not having been definitely 
collected with this object in view. 
In all of the experiments described above sea-salt was used as the 
plasmolysing medium, but in one experiment with Hormidium (XXIX) 
40 per cent, sucrose was employed. In the fresh material (1,000 cells 
counted) there were 88*7 per cent, strongly, and 11*3 per cent, slightly, 
plasmolysed cells, none being unaffected. After two days in a desiccator 
over 34-5 per cent, sulphuric acid the result of the count (378 cells) showed 
4*6 per cent, slightly plasmolysed and 95*4 per cent, unaffected cells ; none 
were strongly plasmolysed and about three-quarters of the cells were dead. 
Th is may be compared with the result of Experiment XIV. 
