ir. DICTYOTACEtE.— DicTYOTA. 109 



abundant In my specimens, between wliich scattered spores are often found. In 

 very many specimens the position of tbe sori is occupi ^d by a line of proliferous 

 papillae or cilia of greater or less length. 



I have some doubts w' ether I am correct in referring the Florida plant to 

 D. Fasciola, Lam., to which, if it be different, it approaches very closely. I have 

 compared it with ]\Iediterranean specimens, but not with ve y well preserved or 

 sufficiently developed ones ; and the agreement in most respects is very great. But 

 there is considerable difference in aspect among the Key West specimens, so much 

 that at first I referred them to two species, in one of which the frond is fastigiate, 

 and regularly dichotomous ; in the other, having more virgate branches, pinnatifido. 

 dichotomous. On comparison of a great number of specimens, I do not find this 

 diflference in branching sufficiently constant. The figures of Roth and Esper, 

 quoted above, are very rude. The present species is what was formerly doubtfully 

 referred, on my authority, to D. linearis, Ag., and published by Prof. J. W. 

 Bailey, as such, in his list of North American Algos. 



Plate VIII. B. Fig. 1, Plant of Dictyota Fasciola ; the natural size ; fig. 2, 

 portion of a segment, with spores, and tufts of anther idia ; fig. 3, portion of a 

 similar segment with papillas ; both magnified ; fig. 4, small portion of a segment, 

 with scattered sjiores and tufts of paranemata ; showing also the surface cellules, 

 and the lines defining the large internal cells ; highly magnified. 



2. Dictyota dichotoma, Lamour. ; frond repeatedly dichotomous, broadly-linear, 

 (1 — 4 lines broad) membi'anaceous ; the axils narrow and subacute ; lacinite erecto- 

 patent, gradually narrower towards the extremities ; the margin entire ; the apices 

 obtuse or emarginato-crenate ; sori and scattered spores dispersed over the medial 

 region of the segments, leaving an unoccupied space within each margin. J. Ag. 

 Sp. Alg. vol. 1, p. 92. Harv. Phyc. Brit. t. 103. Ulva dichotoma, Huds. — E. Bot. 

 t. 774. Dictyota imlgaris, and D. dichotoma, Kiitz. Sp. Alg. p. 553, 554. Bicho- 

 phyllum, Kiitz. Phyc. Gen. p. 337. 



Hab. On stones and sea plants in tide pools. Rare. At Charleston, gi'owing 

 on old submerged wood-work at SuUivan's Island, Prof. Lewis E. Gibbes, Key West, 

 W. H. H. (v. V.) 



Fronds tufted, but not very densely clustered, from three to six inches long or 

 more, varying much in breadth ; ordinarily three or four lines in breadth, but 

 sometimes much narrower and occasionally wider, sevei-al times dichotomous ; the 

 segments at each successive forking becoming narrower. In some varieties, the ulti- 

 mate segments are very narrow and constantly spirally twisted ; in the ordinary 

 forms they are flat, and not much narrower than the lower ones. The axils are 

 narrower than in the preceding species and the segments less widely spreading ; 

 and the apices are decidedly obtuse. The substance is thin and membranous, semi- 



