IV. 
DICTYOTACEiE. — Dictyota. 
109 
abundant in my specimens, between which scattered spores are often found. In 
very many specimens the position of the sori is occupi cd 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 , Lain., to which, if it be different, it approaches very closely. I have 
compared it with Mediterranean 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 Ivey 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 
difference 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 J). linearis , My., and published by Prof. J. W. 
Bailey, as such, in his list of North American Alga3. 
Plate YIII. B. Fig. 1, Plant of Dictyota Fasciola ; the natural size ; jig. 2, 
portion of a segment, with spores , and tufts of antheridia ; jig. 3, portion of a 
similar segment with papillae ; both magnijied ; jig. 4, small portion of a segment, 
with scattered spores and tufts of paranemata ; showing also the surface cellules, 
and the lines defining the large internal cells ; highly magnijied. 
2. Dictyota dichotomy, Lamou-r.; frond repeatedly dichotomous, broadly-linear, 
(1 — 4 lines broad) membranaceous ; the axils narrow and subacute ; laciniae 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 , Fduds. — E. Bot. 
t. 774. Bictyota vidgaris, and I). dichotoma , Kiitz. Sp. Alg. p. 553, 554. Dicho- 
phyllum , Kiitz. Pliyc. Gen. p. 337. 
Hab. On stones and sea plants in tide pools. Rare. At Charleston, gTO wing- 
on old submerged wood-work at Sullivan’s Island, Prof. Lewis II. 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, several 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- 
