MARINE ALG OF BEAUFORT, N. C. 399 
It is worthy of note that Petalonia and Hypnea, which at other seasons are restricted 
to the zone below low water, now extend into the zone between the tide lines. 
With the vertical distribution so limited, there is naturally little opportunity for 
the formation of distinct zones other than those occasioned by the growth of species 
above or below low water. While some species occur at slightly greater depths than 
others, the difference is so slight that it is scarcely capable of description. 
HORIZONTAL. 
The horizontal distribution is marked by a decrease in the number of both species 
and individuals as we go from the inlet in any direction, whether into the harbor, into 
Bogue Sound, or into Back Sound. The summer flora is the only one that has been 
studied in this connection. At this time the Fort Macon jetties bear a dense 
growth, Padina, Hypnea, and Chondria dasyphylla being the dominant forms, closely 
followed by Dictyota and Sargassum, bearing an abundance of Acrochetium and Herpo- 
siphonia, with Gymnogongrus, Codium, and Gracilaria multipartita occurring in consider- 
able numbers and other species occasionally present. Between the jetties are numerous 
plants of Rosenvingea, Chondria sedtfolia, and Dermatolithon pustulatum on eel grass 
(Zostera marina), while the innermost jetties bear an abundance of Fucus. Lyngbya 
confervoides and Gelidium cerulescens cover the rocks and shells between tide lines on the 
jetties and along the shore. 
On Shackleford jetties the same species are found except that Chondria dasyphylla 
is lacking, probably because this brittle species is unable to endure the strong tidal 
currents found there. Padina is the dominant species at this place, occurring with 
Sargassum in great fields on the rocks in this clear water to a depth of 1.4m. Gracilaria 
multipartita is more abundant than on Fort Macon jetties and G. confervoides is present 
‘in large numbers. Rosenvingea, Fucus, and Chondria sedifolia were not observed here. 
Many plants of Padina growing in the most brightly lighted situations were slightly but 
decidedly calcified, while the majority of the plants here and all of this species observed 
elsewhere lacked this deposit. 
Along the shore from Fort Macon jetties to Bogue Sound no algae were found, prob- 
ably because of the lack of places suitable for attachment, since the conditions here 
appear especially favorable for algal growth. 
Of the 77 species and varieties recorded for the harbor, 65 have been found growing 
on the jetties and buoys near the inlet; the 12 species not found here being as follows: 
Chroococcus turgidus? Chztomorpha linum. 
Hydrocoleum lyngbyaceum. Chzetomorpha brachygona. 
Lyngbya lutea. Bryopsis plumosa. 
Oscillatoria nigro-viridis. Ectocarpus duchassaingianus. 
Ulva fasciata. Stilophora rhizodes. 
Ulva lactuca var. latissima. Laurencia tuberculosa var. gemmifera. 
