of Terrestrial Algae. II. 699 
Table VIII). A marked feature, moreover, of our consecutive estimations 
of Pleitrococcus subjected to drought has been the peculiar variability of the 
figures at successive periods, of which both Table VIII and Fig. 6 afford 
testimony. Yet Table IV demonstrates that the error in the case of Plenro- 
coccus is remarkably small, and one can only conclude that other factors 
come into play which have at present not been recognized. In Experiment 
( Unaffected: - 
K.ey: / Percenfaye of U naf/eoted maferial 
[ Soaked. 0.t f skoistL . . , , . 
XXX, the results of which are reproduced in Fig. 6 , the material was 
kept throughout in the dark and at a constant temperature of i8°C., but 
nevertheless the figures are as erratic as in the other cases. 1 It remains to 
mention that the cells of Pleurococcus show none of that permanent con¬ 
traction of the protoplast during the later stages of drought, such as has 
been recorded above for the filamentous forms ; whenever the material was 
examined in tap-water the living cells looked quite normal. Although few 
experiments have been performed with Cystococais there is every reason to 
believe that its behaviour is similar to that of Ple?irococcus. 
1 An average of 2,000 cells was counted at each estimation (except for the last two) in this 
experiment. A further estimation made after sixteen weeks’ exposure to pure sulphuric acid produced 
no different result, 75-8 per cent, of the cells still plasmolysing. 
