30 THE RELATION OF PLANTS TO TIDE-LEVELS 
and sexual generations, comparable with that of Dictyota and that of the red 
alge Polysiphonia and Griffithsia. (See Lewis, 1914.) 
The vertical distribution of Pylaiella thus far recorded extends from —6 
inches up to 5 or 6 feet. That is, it occurs both in areas where it is nearly 
always submerged and also, on shady spots along wharves, where it is exposed to 
the air from 8 to 9 hours each tide. It seems evident that this alga is not able 
to go higher on the wharves, nor, in most places, even as high as here recorded, 
because of the danger of desiccation during low tide. It perhaps does not grow 
on bottom below mean low water at the Inlet because of the swift current 
which runs over the bottom, sweeping along pebbles, shells, and dislodged 
alge. Why, if it can endure long submergence in fresh water, it does not push 
further up the fresh-water streams, it is not easy to understand, unless it be its 
inability to endure continuous submergence in fresh water. Pylatella would 
probably prove a good subject for experimental determination of the effect, on 
the distribution of alge, of such conditions as high temperature and exposure 
to fresh water and to dry air. 
THE RHODOPHYCE. 
Of the 13 species of this group of alge growing on the bottom of the harbor, 
the most important are Chondrus, Porphyra, and the incrusting alga Hilden- 
brandia. We will discuss these first, and then take up the remaining forms in 
alphabetical sequence. Plate 1x shows the distribution of the most frequent of 
the Rhodophycez about the harbor. 
Chondrus crispus is usually the most abundant red alga in the harbor, after 
the Ceramiums, Hildenbrandia, and perhaps Bostrychia. It occurs abundantly 
in the Inlet during the summer, chiefly on the pebbly bottom east of the 
channel, between 1 foot below and 1 foot above mean low water. In July 1911, 
for example, Chondrus was distributed over a strip varying from 10 to 40 or 
50 feet in width, and stretching from 1,700 to 2,000 north. The plants found 
here are from 0.5 dm. to 1 dm. in height, and form dense tufts of a reddish or 
brownish color. They are apparently quite as vigorous and fruit quite as 
freely as plants growing in open water in the Outer Harbor or in Long Island 
Sound. Two or three smaller plants were found at 1,600 north near mean low 
water. These were the southernmost plants ever recorded. Though this alga 
is one of the most constant in occurrence and distribution during each summer, 
it could not be found after careful search along the Inlet in April 1911. On 
September 28, 1911, this species was not seen, though searched for as carefully 
as possible, when the water was at the +1-foot level. 
Porphyra laciuniata: This is the only red alga found on the bottom of the 
harbor in April 1911. It was then nearly as abundant and widely distributed 
as Ulva, except that it was never found in or near fresh-water streams. ‘The 
Porphyra was then most abundant east of the channel to the Outer Harbor, 
from 1 foot below to 1.5 feet above mean low water. The individual plants at 
this point were often 2 to 3 dm. long, and about as broad. In other parts of 
the harbor, in April, the Porphyra is sprinkled about somewhat generally, 
though not abundantly, chiefly on wharves and wrecks between the 2-foot and 
the 4-foot levels. Hundreds of sheets of this alga, usually 1 to 2 dm. across, 
but sometimes larger, were seen in April among the stubble of the Spartina 
glabra along the west shore. Closer examination showed that the vast majority 
