392 BOTANICAL GAZETTE [JUNE 
the Fisheries Laboratory at Beaufort, N. C.; to Mr. H. D. ALLER, 
Acting Director of the Fisheries Laboratory at Beaufort, N. C., for 
many courtesies extended during this investigation; to Mr. FRANK S. 
Cotitns, Malden, Massachusetts, for verifying the determination 
of the species of Dictyota occurring at Beaufort; to Dr. MARSHALL 
A. Howe, New York Botanical Garden, for information concerning 
Padina; to Mr. I. F. Lewis, Johns Hopkins University, for speci- 
mens of Dictyota from Port Morant, Jamaica; and to Professor D. S. 
Jonson, Johns Hopkins University, for helpful criticisms and 
suggestions. 
CONCLUSIONS 
1. As on the coast of Wales and England, Dictyota dichotoma at 
Beaufort, N. C., produced its sexual cells at regular intervals, bearing 
a definite relation to the tides. 
2. The time of production of these crops, however, differs from 
that on the coasts of Wales and England, the crops being borne at 
monthly instead of fortnightly intervals. 
3. The assumption that light is the sole factor determining the 
time of fruiting does not hold for the plants of Dictyota dichotoma 
growing at Beaufort. 
4. Specimens of Dictyota from Jamaica indicate that there also 
the sexual cells are produced in periodic crops, and that periodicity 
may obtain throughout the genus. The time of fruiting, however, 
at least in some cases, is different from that of Dictyota at Beaufort. 
5. Periodicity in the production of the sexual cells is not universal 
among the Dictyotaceae. A species of Padina, probably P. Dwr- 
villaei Bory, bears antheridial sori of all ages on the same plant. 
Jouns Hopkins UNIVERSITY 
ORE 
LITERATURE CITED : 
1. THuret, G., Recherches sur la fécondation des Fucacées et les anthéridies 
des Algues. Ann. Sc. Nat. Bot. IV. 3:5-28. pls. 2-4. 1855. 
2. WitiiAms, J. Lioyp, The iinshicccusete of Dictyota and Taonia. Annals of 
Botany 11:545-553. pl. 25. 1897. 
3- ———,, Reproduction in Dictyota dichotoma. Ibid. 12:559-560. 1898. 
4: , Studies in the Dictyotaceae, II. The cytology of the gametophyte 
peneration: Ibid. 18: 183-204. pls. 12-14. 1904. 
, Studies in the Dictyotaceae, III. The periodicity of the sexual cells 
in Dichiote dichotoma. Ibid. 19:531-560. 1905. 
6. U. S. Coast and Geodetic Survey, Washington, Tide Tables for the year 1906. 
5. 
