of Terrestrial Algae. II. 713 
meability to the stain sets in. It will be seen that, if the drought is suffi¬ 
ciently prolonged, all the cells may ultimately take up the stain (series 2). 
A further noteworthy point is that soaking of the material with water, after 
a brief period of drought, leads to a more or less rapid decrease in the per¬ 
centage of stained cells (cf. series 1 and 3), whilst there is no such decrease 
if the drought has been prolonged (series 2). This falls into line with the 
observations detailed above on the recovery of drought material when 
placed in damp air (cf. p. 709), where in the vast majority of cases the pre¬ 
vious drought was as intense or even more intense than in series 2. Dilute 
erythrosin gives quite similar results to those described for eosin, but no such 
alteration in the behaviour of the protoplasts with respect to neutral red, 
such as is recorded below for Hormidimn , was found in the case of Zygo- 
gonium ; ten minutes’ treatment with o-2 per cent, neutral red stained all the 
cells, and even after three days’ drought there was no change in this respect. 
Table XVI. 
Percentages of cells 1 stained and unstained by neutral red (treatment as 
described in text) in Hormidium during drought and subsequent 
recovery. 
(Experiment XXXII, habitat II.) 
Scries i. 
A. 
Series 2. 
A 
'Whole 
Protopl. 
Whole ' 
' Whole 
Protopl. Whole 
stained. 
stained. 
unstained. 
stained. 
stained, unstained. 
Original material 
1 day’s drought 
25*5 
8*3 
66*2 
25-6 
36-0 
38-4 
11 -3 
5*2 
83-5 
— 
— 
— 
2 days’ „ 
0-0 
i -5 
98-5 
4.9 
3 -i 
92-0 
3 ?> 
— 
— 
— 
1.2 
9.4 
89-4 
5 >> >> 
— 
— 
— 
0-2 
•10-0 
99-8 
3 days after soaking 
— 
— 
— 
7-5 
19-2 
73 ‘° 
2. Hormidium. This alga gives results with 0-2 per cent, eosin and 
dilute erythrosin which are identical with those obtained for Zygogonium , 
the healthy cells of fresh material altogether excluding the stain, whilst 
nearly all the cells of drought material take it up rapidly. Neutral red 
affords different results. With this stain the cells fall into three groups, 
viz. those which are unstained, those with the protoplast but not the chloro- 
plast stained, and those in which the whole contents are stained. 
The effect of drought is rather contrary to expectation (cf. Table XVI). 
The material in this case was stained for 10 minutes in 0-4 per cent, 
(series 1) or 02 per cent, (series 2) neutral red dissolved in tap-water, the 
estimation again being made in tap-water. The conditions of drought were 
the same as in the experiments above described for Zygogonium. I he 
progressive change in the material is again quite obvious, but in this case it 
is in the direction of a decrease to a minimum of the number of stained 
cells. 
1 2,000 cells counted at almost every estimation ; dead cells ignored. 
