of Terrestrial Algae. II. 709 
Its relation to the same strength of plasmolysing solution as had been 
used foi the previous drought determinations was investigated a few 
days later. Some of the results are epitomized in Table XIII (cf. also 
Table VI and Figs. 6 and 8). Although in most cases some alteration in 
the behavioui of the material was to be recorded, a pronounced recovery 
was only observed when the duration of the previous drought had been short, 
as in the case of the Prasiola and protonema. In such cases, moreover, the 
recovery is rapid, and one can feel sure that it is actually due to an altera¬ 
tion of the cells that had previously been affected by the drought. On the 
Fig. 8. Recovery from drought in the case of Zygogonhim (Expt. XVI). 
other hand, if material during exposure to drought has once reached the 
state in which a large number of the cells exhibit the slight permanent con¬ 
traction of the protoplast mentioned on p. 691, recovery is very slow, and one 
is in some doubt as to whether increasing plasmolysis is due to an actual 
recovery of the tendency to plasmolyse or to the gradual formation of new 
threads by some of the surviving normal cells. 1 Those recovering from 
drought, however, are generally distinguished by microscopic characteristics 
(cf. p. 715) from those due to new growth. That there is an actual recovery, 
even in such cases, is indicated by observations made in Experiment XVI 
(cf. Table VI and Fig. 8), where the gradual increase in the number of 
slightly plasmolysed cells proved to be due to an actual increase in the 
1 Moreover, when recovery is slow, the deleterious effect of laboratory conditions (cf. p. 716) 
may be just as responsible for the state of the protoplast as the original drought. 
