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BULLETIN OF THE BUREAU OF FISHERIES. 



the plants reaching a size of 22 cm. ; Chondria sedifolia has appeared, and one small mass 

 of Rhodymenia palmetto, was found on Fort Macon jetty. 



By June the spring flora has disappeared and the summer flora is established. The 

 growth of the summer species at this time is very rapid. On May 14, 1909, the jetties 

 at Fort Macon were carefully searched for Dictyota without revealing a trace of this 

 species. On June 9, when the next collection was made, there were found numerous 

 plants 20 to 29 cm. tall which had matured and liberated their sexual cells. The species 

 present now include well-developed fruiting plants of Codium, Dictyota, Padina, Hypnea, 

 Chondria dasyphylla, C. sedifolia, and Herposiphonia, and plants of Rhodymenia 6 cm. 

 tall. None of the spring species was collected at this time. 



All of the summer species are present before the first of July and maintain them- 

 selves until the following October or November. 



From these facts we can picture the seasonal succession as follows : With the advent 

 of colder temperature, the summer flora begins to disappear by the middle of October, 

 the larger number of the species disappearing by November or December, others dropping 

 out with each successive month, but some remaining until February. The first of the 

 spring flora makes its appearance in November, other species appearing with each 

 successive month, the flora, however, remaining relatively sparse during the winter, the 

 smallest number of species being found in March. With the coming of warmer tempera- 

 ture, this flora becomes more abundant and reaches its greatest profusion in April, after 

 which time it begins to dwindle and disappears by June. The first of the summer flora 

 appears in April, others appear in May, and all are present before the last of June. 



If the seasonal behavior of the algae is compared with the recorded water tempera- 

 ture, it is observed that the disappearance of the summer flora in October and November 

 is coincident with the greatest decrease in temperature; the appearance of the spring 

 flora in November and the succeeding months follows this diminution; the time of 

 greatest scarcity of algae, in March, follows the lowest minimum temperature reached; 

 the rapid increase of the spring flora to its maximum in April is coincident with the 

 greatest increase in temperature, while its disappearance during May is coincident with 

 the continued increase; and the appearance of the summer flora in April is coincident 

 with this greatest increase and its profusion in June follows this great increase of tempera- 

 ture. It would scarcely be possible to find a more direct relation between temperature 

 and the seasonal distribution of plants than is shown here. From this it seems evident 

 that, while light probably has its effect, the seasonal distribution of algae is determined to 

 a very great extent by the temperature. More exact studies would probably show 

 interesting relations between the temperature and the individual species occurring here. 



The manner in which the summer species exist during the winter and the spring 

 species exist during the summer at this place has not been determined. During the 

 seven summers spent at the Beaufort laboratory, two small plants of Grinnellia and a few 

 small plants of Dasya have been observed, but no other of the spring species has been 

 found here after May, and none of the summer species has been, found after February. 

 Lewis (1914) has shown that, at Woods Hole, Mass., many of the summer species of red 

 algae occurring there (Dasya, Polysiphonia, and others) persist during the winter by 

 means of the minute holdfasts of sporelings, the other portions of these sporelings and all 

 of the older plants dying at the approach of cold weather. The plants arising from these 

 holdfasts the following summer were mainly tetrasporic. Probably some such method 



