36 THE RELATION OF PLANTS TO TIDE-LEVELS 
Enteromorpha clathrata: The occurrence of this species as an epiphyte we 
have already mentioned when referring to the long, streaming tufts of it on the 
Zostera as the source of the loose mats of this alga that drift over the bottom. 
We may here emphasize the fact that it is very abundant as an epiphyte. Often 
a dozen large tufts of it may grow on a single leaf-cluster of Zostera, and the 
filaments may attain a length of several decimeters before being set free, which 
usually occurs by the rupture of the supporting leaf. H. clathrata also has a 
wide distribution. It is the only noticeable epiphyte on the outlying clumps 
of Zostera, except a few tufts of Melosira. 
RHODOPHYCE. 
As indicated in our enumeration of species, only two epiphytic red alge © 
have been found in the harbor, and both belong to the genus Ceramium. 
Though Polysiphonia occurs as an epiphyte on Zostera in other Long Island 
waters, mature plants of this species never have this habit in our harbor. 
Melobesia, another epiphyte found in more saline waters about Long Island, 
does not occur here at all. 
Ceramium rubrum: This alga‘ forms dense tufts, 5 to 10 cm. long, on the 
leaves of Zostera. Dozens or scores of these large tufts may sometimes be seen 
on each square meter of the Zostera, and in such areas this Ceramium is the 
most prominent epiphyte. This alga is most abundant just aside from the 
swiftest current along the Inlet, about the deep hole, and beside the tide- 
stream entering the latter from the northwest (plate Ix). Evidently this red 
alga, like Melosira, flourishes best in moving water. In fact, the Ceramiwm 
fails to accompany the Zostera to the limit of its distribution, the outer or upper 
third of the Zostera being bare of the alga. Some of the plants of this Ceramium 
found in July and August bore tetraspores and others cystocarps or antheridia. 
Ceramium strictum: This is the only red alga of the Inner Harbor which has 
. been found here solely as an epiphyte. It is somewhat smaller in size and 
brighter in color than C. rubrum. The distribution of C. strictum is in general 
similar to that of C. rubrum, but it is evidently still more closely confined to the 
Zostera immediately surrounding the deep hole and the tide-stream flowing 
into it from the northwest. } 
So far as has been determined from a study of the epiphytic alge of the 
harbor bottom, a study which has been concerned especially with the Ceramiums, 
these alge are found at levels where they are submerged at all but the lowest 
tides. They evidently will not endure long exposure to dry air. The absence 
of the Ceramiums from the Zostera growing in the area from 500 to 700 north 
by 200 to 600 east indicates that these alge can not endure submergence in the 
brackish, and for part of the time actually fresh, water which flows from the 
Creek at low tide. 
3. THE MID-LITTORAL BELT (1.5 TO 6.5 FEET). 
As one looks about the harbor at low tide the whole natural shore for some 
distance below high-water level is seen to be occupied by a very clearly marked — 
belt of vegetation of quite uniform character. Closer examination shows that 
the sole conspicuous plant of this green belt is the salt reed-grass Spartina 
glabra var. alterniflora, and that it really occupies the middle portion of the 
strip of muddy shore between the two tide-marks. In fact, except where 
