MARINE ALGJE 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 afiy 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 Acrochaetium 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 sedifolia, and Dermatolithon pustulatum on eel grass 

 (Zostera marina), while the innermost jetties bear an abundance of Fucus. Lyngbya 

 confervoides and Gelidium ccerulescens 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 1.4 m. 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? 

 Hydrocoleutn lyngbyaceum. 

 Lyngbya lutea. 

 Oscillatoria nigro-viridis. 

 Ulva fasciata. 

 Ulva lactuca var. latissima. 



159321 20 3 



Chaetomorpha linum. 



Chsetomorpha brachygona. 



Bryopsis plumosa. 



Ectocarpus duchassaingianus. 



Stilophora rhizodes. 



Laurencia tuberculosa var. gemmifera. 



