724 Fritsch and Haines.—The Moisture-relations 
period of drought has not been too prolonged, there is, in the case of the 
algae, an increasing percentage of unstained cells during the days succeeding 
access of moisture. 
14. In Hormidium there is a progressive decrease in the number of 
cells stained with neutral red during a period of drought, the decrease being 
evident in both the categories above distinguished (cf. 11). If the material 
is wetted before the drought has lasted too long, there is a reversal. There 
is no obvious difference in the staining reactions with eosin of fresh and 
of drought material of Pleurococcus. 
15. Material of Zygogonium and protonema that has been in a sealed 
slide shows staining properties similar to those of drought material. 
1 6. Three kinds of cells are distinguishable in drought material of the 
filamentous forms, viz.: (a) dead cells; ( b ) living, though perhaps in part 
moribund, cells which have a rigid, slightly contracted protoplast and, in 
the algae, contain coarse granules ; (c) healthy green cells, in the algae 
commonly provided with numerous fine peripheral granules, with an uncon¬ 
tracted protoplast which, like that of the cells under ( b ), is not affected even 
by strong (25 per cent, sea-salt) plasmolysing solutions. The same types of 
cells are recognizable in material that has been for some days in a sealed 
slide. The second kind of cell also appears at times in material that has 
been for a prolonged period in the laboratory or exposed to strong illumina¬ 
tion. Such cells have not been observed in Pleurococcus. 
17. Examination with dark-ground illumination shows that the ( b ) 
and (c) cells possess a living protoplast which is not coagulated, but no 
Brownian movement is to be recognized within it, and, by contrast with fresh 
material of Zygogonium , Hormidium, and the protonema, the cells fail to 
show any vacuoles. Even fresh material of Prasiola and Pleurococcus 
exhibits these characteristics, which in the other forms are only to be seen 
in the drought condition. 
18. If fresh material of these different forms is centrifugalized for 
a quarter of an hour at 2,500 revolutions to the minute the chloroplasts and 
nuclei are found to be displaced towards one side of the cell in all the 
filamentous forms except Prasiola , the granules, when present, creaming in 
the opposite direction. Drought material is, however, unaffected even by 
an hour’s centrifugalizing. Fresh material of Pleurococcus and Prasiola 
behaves just like drought material of the other forms—that is to say, one 
hour’s centrifugalizing produces no effect. 
19. The granules found in the cells of these terrestrial forms probably 
in large part consist of fats, which, however, appear to vary somewhat in 
their solubilities in the usual fat solvents. At the same time in all the algae 
investigated, except Prasiola , we have obtained evidence for the presence of 
a second type of granule, characterized by small size, usually peripheral 
distribution, and the assumption ol a dark, almost black colour after treat- 
