no DICTYOTACEA.—DicTTOTA. iv. 



transparent, and the areolations visible with a moderately powerful pocket lens ; 

 they vary in shape and in size in different parts of the membrane, and I fear scarcely 

 afford a satisfactory specific character. I have not seen fruit on American specimens. 

 On the European plant two sorts of fruit have been noticed, on different individuals : 

 first, oval clusters of spores, covered at first by a common vesicular membrane ; each 

 spore when ripe containing four sporules in a hyaline perispore ; second, solitary, 

 roundish, simple spores scattered over the surface. The colour is olivaceous, some- 

 times greenish and sometimes brownish. 



3. DiCTYOTA ciliata, J. Ag. ; frond woolly at the base, repeatedly dichotomous, 

 broadly linear, membranaceous ; the axils rounded ; lacinise patent, linear, gradually 

 narrower towards the extremities ; the margin ciliate, with distant, awl-shaped, 

 slender teeth ; the apices obtuse ; spores forming minute sori scattered over the 

 middle region of the lamina, leaving an unoccupied space within each margin. 

 J. Ag. Symb. 1. p. 5. Sp. Alg. vol. 1. p. 93. Kiitz. Sp. Alg. p. 556. (Tab. VIII. A.) 



Hab. On Alg£e and corals near low-water mark. Florida Keys, abundant at Key 

 "West, Dr. Wurdemann, Dr. Blodgett, W. H. ZT., ^-c. (v. v.). 



Root and lower part of the frond coated with curled, woolly hairs. Fronds densely 

 tufted, six to eight or ten inches in length, from an eighth to a quarter-inch in 

 breadth, many times dichotomous ; the lacinia3 gradually narrower in the upper 

 dichotomies, ciliated at intervals of a few lines with slender, subulate, tooth-like 

 processes. These are more abundant in some specimens than in others. The axils 

 are rounded ; the lower ones spread widely and the upper are gradually narrower. 

 The apices are subacute, or blunted. The sori consist of a few spores, irregularly 

 grouped together, and scattered over three-fourths of the surface of the lacinias, 

 leaving a narrow unoccupied portion down each margin. Sometimes the frond is 

 pitted, (as shown at fig. 4,) the pits apparently caused by the falling off of the 

 sori, carrying with them the surface cells. The colour is a clear brown olive, 

 greener toward the tops ; and the substance is membranaceous, shrinking in drying. 

 Eeadily known, in most cases, by the ciliate margins ; but sometimes nearly entire^ 

 in which case it may be mistaken for D. dichotoma. 



Plate YIII. A. Fig. 1. Plant of Dictyota ciliata ; the natural size ; Jig. 2, 

 part of a segment, with sori, and Jig. 3, part of a segment from which the spores 

 have fallen, leaving pits ; both magnified ; fig. 4, small portion of the surfoce, with 

 sorus^ showing the small surface cellules, and the lines defining the large internal 

 cells : highly magnified. 



4. Dictyota JBartayresiana^ Lamour. ; frond scarcely woolly at the base, repeat- 

 edly dichotomous, linear, coriaceo-membranaceous, very entire ; the axils rounded ; 



