TEMPERATURE OF WATER 147 
1912) in the study of the New Jersey marshes. It is hoped that the results of 
these determinations may be presented in a later paper by the junior author of 
this one. 
5. THE TEMPERATURE OF THE WATER. 
On the subject of the temperature of the water also we have no quantitative 
results to present. A few measurements of the temperature at the bottom and 
at the surface of the middle of the Inner Harbor at high tide (of 7.5 feet) were 
taken in July 1909, which showed a difference of but 1° or 1.5° C. In Miss 
Streeter’s records made in July, the temperature of the stream at 600 south by 
720 east was found to vary from 9° C. at low tide to 18° C. at high water. Itis 
evident of course, that plants like Zostera, Ruppia, Ulva, etc., which lie on the 
black, heat-absorbing mud in the sun at low water, must often be heated to 30° 
or 35° C. or higher, in the summer. When, on the contrary, these plants are 
exposed at night, their temperature must fall at least to 10° C. or lower, since 
the air temperature may go down to 8° or lower during the growing season. 
Just what part the seasonal change of water-temperatures plays directly, in 
determining the seasonal development of the alge of the bottom, can not yet 
be stated. It is a well-known fact that the algal flora of a given locality varies 
markedly from winter to summer. In Section III of this paper it has been 
pointed out that not only are certain of the characteristic summer forms wanting 
in April and December, but in the former month, at least, Ulva, one species of 
Ectocarpus, and Porphyra were far more abundant in the Inlet than they have 
ever been in the summer. The rockweeds all about the harbor, which in summer 
bear practically no epiphytes, were found densely coated with filaments of 
Ulothriaz flacca. In just how far the low temperatures of winter are directly 
responsible for the abundance of these alge in winter, or whether they may be 
indirectly responsible by affecting the evaporation, has not yet been ascertained. 
Possibly, as Warming suggests (1909, p. 151), experimental physiological study 
may show that the larger proportion of dissolved O and CO, held by the water 
when cold offers the real explanation of the greater abundance of certain species 
in winter. The whole subject of the winter activities of marine plants is 
greatly in need of continuous study, such as has now become possible, with our 
many well-equipped marine laboratories. 
