6g6 Fritsch and Haines .— The Moisture-relations 
especially Figs. 2 and 3), whilst the percentage of unaffected cells for the 
first day or two increases but little. Subsequently the number of slightly 
plasmolysed cells again decreases, and that of the unaffected cells rises 
rapidly (cf. Figs. 1-3). In the case of moss protonema the same 
relation holds good (Fig. 5), but here the appearance of permanent con¬ 
traction in many of the cells (cf. p. 694) ultimately leads again to an apparent 
increase in the numbers of slightly plasmolysed and a decrease in the 
number of unaffected cells. In these forms, therefore, there is evidently 
a gradual loss of the tendency to plasmolyse, many of the formerly 
Fig. 5. Influence of drought on plasmolysis of moss protonema (expt. XV). 
strongly plasmolysed cells, during the first days of a period of drought, still 
exhibiting slight plasmolysis. In the final stages, however, the majority 
show no plasmolysis. 
In the case of the filamentous forms the behaviour during drought nearly 
always follows the sequence just described and irregularities were rarely 
noticed. In some of the earlier experiments, where the material was merely 
dried by exposure to the air of the laboratory, certain variations were, how¬ 
ever, noticed which appear to be related to changes in the humidity of the 
air. Thus, after a week’s drying in the laboratory, the Hormidium in 
Experiment VI gave on Feb. 20: 6*6 per cent, strongly plasmolysed, 53 * 1 
per cent, slightly plasmolysed, and 40*3 per cent, unaffected cells ; on 
Feb. 27, however, the figures were: 19-4 per cent, strongly plasmolysed, 
