IV. DICTYOTACE.E.— DicTTOTA. Ill 



laciniffi spreading, especially the upper ones ; apices divaricate, the younger ones 

 sharply bifid, each lobe acuminate ; spores forming minute sori scattered over the 

 whole surface of the lamina. — J. Ag. Sp. Alg. vol. 1, p. 94. Kiitz. Sp. Alg p. 554. 

 (Tab. VIII. C.) 



Hab. Tropical. Coast of Mexico, at Vera Cruz, Liehman ! (v. s. in Herb. 

 T.C.D.). 



Frond three or four inches long, one or two lines in diameter, of nearly equal 

 breadth throughout, many times dichotomously divided, with rounded axils and 

 spreading segments. The uppermost divisions are more or less divaricated. The 

 margin is entire and flat. The young apices are sharply notched or bifid ; each 

 notch deltoid-acuminate, ending in a sharp point. The sori are minute and 

 densely dotted over the whole surface. In our specimen they have fallen away, 

 leaving cavities in their place. The substance of the frond is thickish, somewhat 

 coriaceous, and the structure is denser than in some other species. The surface 

 cellules are minute ; the areolations beneath them not much longer than their 

 breadth. In drying, this plant does not adhere to paper. Known by its sharply 

 bifid apices from any state of D. fasciola or D. dichotoma. Distinguished from 

 D. acutiloba by the widely scattered fructification. 



Plate VIII. C. Fig. 1, Plant of Dictyota Bartayresiana ; the natural size ; fig. 

 2, apex of a segment, magnified ; fig. 3, extremity of the same, with depressions from 

 which sori have fallen, and showing the surface cellules and internal cells ; highly 

 magnified. 



5. Dictyota crenulata.^ J. Ag. ; frond woolly at the base, repeatedly dichotomous, 

 coriaceo-membranaceous, with patent, but not very blunt axils ; lacinias linear, 

 undulate ; the margin eroso-dentate, the toothlets close together and of unequal 

 size ; apices very blunt, lingulate ; sori at length occupying the whole surface. 

 /. Ag. Sp. Alg. vol. \,p. 94. Kiitz. Sp. Alg. p. 558. 



Hab. Tropical. At St. Augustin, on the Pacific coast of the Mexican Kepublic, 

 Liebman ! (v. s. in Herb. T. C. D.). 



Fronds tufted, 2 — 4 inches high, about one and half or two lines in breadth, gra- 

 dually wider from the base upwards, many times closely dichotomous ; the segments 

 spreading, the whole frond having a fan-like outline. The sinuses betwen the lacini^ 

 are rounded, though not conspicuously so, and the upper ones are rather narrow. The 

 margin is undulated, and closely eroso-denticulate, or jagged with unequal, deltoid, or 

 subulate, tooth-like processes. The apices are rather wider than the portions below 

 them, and so blunt as to be almost truncate. The young ones are obtusely emar- 

 ginate. The sori are small, at first foi-ming patches here and there, but eventually 



