ENHALID FORMATION oo 
Polysiphonias, Rhabdonas, Ulvas, etc., which, with their anchoring pebbles, 
were evidently in transit through the Inlet. From a careful consideration of 
the conditions existing in the deeper portions of the harbor, it seems evident 
that the absence of Zostera is in some way determined by the swift tidal 
currents rushing over these portions. As there is no reason to believe that this 
current acts directly on the Zostera, it seems clear that the current acts by 
forming an unstable and sterile bottom on which Zostera can not establish 
itself. A merely sterile soil we would expect to be conquered by the gradual 
extension of Zostera into it, with an accompanying accumulation of organic 
matter about its shoots. We must conclude, therefore, that the downward 
spread of Zostera in this harbor is prevented by a shifting of the soil so frequent 
as to make it impossible for the out-pushing rhizomes to establish themselves 
and thus bind the soil. , 
Ostenfeld, in his study of Zostera in Danish waters, found that the shoots 
are perennial, and the leaves remain green all winter. The winter leaves of 
plants growing on mud bottom do not attain as great a length as leaves 
developed in summer. 
A somewhat similar retardation of growth in winter seems to occur at Cold 
Spring Harbor. Since our observations were confined largely to the months 
of July and August, we can not speak with certainty concerning the activities 
of the Zostera in winter. On April 7, 1911, however, an abundance of 
Zostera plants was found with most of the leaves only 1 or 2 dm. long, and 
evidently young, but also with older leaves a half meter or more in length. 
Plants collected in about the same locality on July 11, 1911, had leaves 2 
meters long. Many of these were dead and worn at the tip and seemed evidently 
more than 2 or 3 months old. Not many plants of Zostera were collected and 
measured in April 1911, but it seems probable, from the condition of the plants 
in the following July, that longer leaves would have been found by more 
thorough search in April. From all the evidence gathered we are led to 
conclude that while the longer leaves of Zostera plants may be torn off by waves 
and ice during the winter, the leaves of the more sheltered plants may often 
persist from fall to spring. This conclusion is strongly supported by the fact 
that the floral shoots certainly persist over winter. This is shown by the fact 
that floral shoots 90 cm. long and bearing fruits 3 to 4 mm. long were collected 
on April 4, 1913, by Dr. A. F. Blakeslee; also by the presence in early July of 
empty spathes on infloresences which higher up bear mature and young fruits 
and unopened flowers. On the Danish coast, according to Ostenfeld, the floral 
shoots are initiated in April and drop off the rootstock in the late fall. We are 
not prepared to suggest any causal explanation for this difference in behavior 
of the Zostera in these two localities, unless it be the more destructive effect of 
winter waves in the more open water where Ostenfeld’s plants grew. 
In brief summary of the facts concerning the distribution of Zostera in the 
Inner Harbor, we can say Zostera commonly occurs on bottom between mean 
low water and 3 feet below this. In one or two areas flooded by streams at low 
tide, a dense stand of Zostera may grow on bottom a few inches above mean low 
water. The extreme upper limit at which Zostera was found—a few plants 
only—is 1.5 feet, and the extreme lower limit is —4.5 feet. The species is 
almost entirely confined to muddy bottoms. 
The part played by Zostera as a substratum for epiphytic alge will be 
noted in discussing the distribution of the alge. 
