1918] TRUE—MARINE ALGAE 79 
a total salt content of about 3.85 per cent, a value which agrees 
very well with these findings. 
In rgo1 REED (19) made a series of Naebclvas determinations 
with marine algae at Woods Hole and in solutions made up with 
distilled water found the following osmotic values: Cladophora (sp. 
not given): NaCl isosmotic with 0.7 gm. mol. NaCl by volume, 
roughly equal to 31.5 atmospheres at 18° C.; cane sugar isosmotic 
with 0.8 gm. mol. by volume (0.965 gm. mol. by weight), equal to 
25 atmospheres of pressure at 18° C. Chaetomorpha (sp. not given): 
NaCl isosmotic with 0.9 gm. mol. by volume, equal to about 40.5 
atmospheres at 18° C.; cane sugar isosmotic with 0.9 gm. mol. by 
volume (1.11 gm. mol. by weight), equal to about 29.5 atmospheres 
at 18 
Osmotic surplus in marine algae 
In order to ascertain the turgor pressure of the marine algae, a 
comparison between the osmotic value of the cells and that of the 
sea water itself is necessary. To facilitate such a comparison these 
values are brought together in table II. For such a calculation as 
TABLE II 
OSMOTIC PRESSURES OF ALGAE AT Woops HOLE 
CELL CONTENTS ISOSMOTIC WITH 
ALGAE 
Cane sugar gm. mol. | Sodium chloride gm. | Sea water per cent 
in liter of solution mol. in liter of solution! by volume 
‘ gm. mol. atmos. | gm. mol. atmos. 
Spirogyra elongata........ 0.25 6.7 |. 0:26 7.2 30 
Cladophora gracilis........ { 0.85 { 28.0 { 0.75 { 33-7 | Osmotic pressure 
: eee 0.80 ee ea Ve eG corrected = 
Enteromorplia intestinalis. { 0.90 { BO Pe a ss Bias 22.3 atmos. 
Ch : f 9.70 |f 31-5 
aetomorpha Linum. .... 0.9 39-7 |) 9.80 { 36.0 
that here required it is important to adopt a correct osmotic value 
for sea water. For purposes of this paper 22.3 atmospheres, cor- 
responding to a sea water concentration of 2.93 per cent total salt, 
is adopted. A glance at the daily density readings made by the 
United States Fish Commission shows a considerable variation in 
the salt content of Woods Hole water from time to time, a fact that 
