MARINE AU>;E OF BEAUFORT, N. C. 395 



carried the species over the unfavorable seasons at Beaufort. The rocks on which 

 Dictyota and Padina grew the preceding summer and on which they occurred abund- 

 antly the following summer were carefully searched by the author under favorable 

 conditions in April, 1908, without revealing a trace of these species. It is probable, 

 however, that a microscopic examination would show these and other algae present on 

 the rocks below low water. 



It is interesting to note that, although cystocarpic and tetrasporic plants of Hypnea 

 are present in the summer in about equal numbers, a collection of 55 plants of this species 

 taken at random in October showed 45 tetrasporic plants and 10 sexual ones, and all 

 the fruiting plants observed in April were tetrasporic. Lewis (1914) has shown that the 

 preponderance of tetrasporic plants in the early summer exhibited by the annual red 

 algae at Woods Hole is due to the fact that the two generations are produced alternately, 

 the last crop of the summer being prevailingly sexual, and the carpospores borne by this 

 crop producing the sporelings whose holdfasts persist through the winter. The peren- 

 nial algae at Woods Hole show no such discrepancy in the numbers of sexual and tetra- 

 sporic plants. In the present instance it seems that the tetrasporic plants of Hypnea, 

 a perennial species, are themselves more resistant to cold than the sexual plants. Fur- 

 ther studies are needed x>n this subject both here and in other regions. 



The seasonal life cycle of Fucus may be summed up here for comparison with other 

 regions. Young plants were observed in April along with large, old, sterile plants. The 

 swollen receptacles become evident about June, but remain small and inconspicuous 

 during July, becoming gradually larger and morp conspicuous during August and Sep- 

 tember, and reaching full size about the latter part of October, the plants showing large, 

 well-developed fruits from November to January or February. After this time all 

 plants observed were sterile. 



It is of interest to note that in May, 1907, when Beaufort Harbor bore almost 

 entirely a spring flora, the coral reef offshore bore such strictly southern forms as Udotea, 

 Dictyota, Zonaria, Nitophyllum, Chrysymenia, and others, along with the spring species 

 of Dasya and Grinnellia, although at this time the water at the depth of this reef was at 

 a lower temperature than that in the harbor. The explanation of this can not be given 

 surely without further study, but certain differences between the harbor and the reef 

 are evident. The greater clearness and higher salinity of the water over the reef probably 

 play a part, but the chief factor probably is that the water at the depth of the reef, as 

 may confidently be believed, does not fall to the low temperature found in the harbor in 

 winter. This suggestion is supported by the species found on Bogue Beach during the 

 winter from December, 1908, to March, 1909. Besides the species growing in the harbor, 

 there were found during this time Zonaria flava, Z. variegata, Nitophyllum medium, 

 Polysiphonia havanensis, and Spermothamnion investiens. The Zonaria variegata and 

 Polysiphonia havanensis were found only once and may have been brought here by the 

 Gulf Stream, but the other three species were not uncommon and may confidently be 

 believed to have come from the coral reef offshore. Codium tomentosum was collected 

 in December and April but not in the intervening months, while Dictyota was not 

 found there until after its occurrence in the harbor in June. Data concerning the condi- 

 tions and algae occurring on the reef in winter would be of considerable interest, since it 

 seems very probable that several species persist there throughout the year. 



