MARINE ALG^B OF BEAUFORT, N. C. 381 



The 124 identified species and varieties recorded for Beaufort have been found as 

 follows : 



As with other plants, two factors determine the algal flora of any region. First, the 

 conditions prevailing at any place naturally exclude all species which are not able to 

 grow under those conditions; second, of the species which are able to grow in any 

 locality, only a part find access to the region and arrive there under conditions favorable 

 for obtaining lodgment. We may be certain that there are hundreds of other species 

 that could grow at Beaufort if they should be carried there. Since, with marine algae, 

 artificial means of transport are usually excluded, the flora which we find in any locality 

 favorable for the growth of algae is determined to a considerable extent by the direction 

 of the currents bringing fruiting plants, fragments, or spores of algae from other regions. 

 Occasionally, however, an alga may be introduced into a region by artificial means. On 

 one occasion there was found in Beaufort Harbor a fragment of Halimeda sp. This 

 seemed a very interesting discovery until it was noticed that there was in the harbor at 

 that time a boat from the West Indies bearing tropical shells and other marine objects 

 for sale. To Jihis boat we may confidently ascribe the presence of the Halimeda. 

 Although this species of alga did not establish itself at Beaufort, its presence there 

 showed the possibility of the distribution of algae by artificial means of transport. 



There is evidence that at least one species has established itself at Beaufort during 

 the progress of these studies. Rosenvingea orientalis, known elsewhere in North America 

 only from Guadaloupe and from Wrightsville Beach, N. C., was first 'found on Bogue 

 Beach in September, 1905, and was not observed in the harbor during that year. The 

 following summer, however, this species was found growing between Fort Macon jetties 

 and on the sea buoy, and in the summer of 1907 it was found on Shackleford jetty as 

 well as on Fort Macon jetties. The records indicate similar facts for a few other species, 

 but are not sufficiently complete to warrant conclusions about them. Miss Dunn (1917) 

 has presented convincing evidence showing that one species of algae, Dumontia 

 filiformis, appeared on the coast of Maine and established itself there between the years 

 1909 and 1913. This species seems now to have spread in considerable abundance 

 along a large part of the New England coast. 



Several species have been found growing in Beaufort Harbor on only one occasion. 

 Such species, while obtaining a foothold, seemed unable to maintain themselves, perhaps 

 because of changing conditions. These may be expected to reappear at any time and 

 may establish themselves. Other species have been found only occasionally, being 

 represented by scattered individuals. Such species seem to be living near the limit of 

 their endurance and may appear and disappear as conditions become more or less favor- 

 able. Still other species, not yet observed here, may be expected to appear whenever 

 chance currents bring them to this region under conditions favorable for their obtaining 

 a foothold. 



