1906] Collins, — New Species in Phycotheca 109 



rapidly than others, so that as the plant grows older it assumes more 

 of the character of a flexuous rachis with alternate branches. The 

 width of the segments varies much, some dense-growing plants 15 

 cm. high having not over 3 mm., while other plants reach 2 cm., the 

 widest part being in the best developed segments about three quarters 

 of the distance from the base. In all cases the segments widen up- 

 wards, even to the terminal ones. 



The older fronds with broad and somewhat sparingly divided seg- 

 ments resemble Dictyota Binghamiana, J. Ag. but the latter does not 

 have the closely diehotomous branching and flabellate outline found 

 in younger plants of Dilophus flabcllaUis. Didyoia Binghamiana^ 

 moreover, is described as having more or less frequent acute, incurved, 

 marginal teeth, which are absent in the present species. Dictyota 

 lifurafa J. Ag. and Dictyota Pappcana Kutz., as figured in Kutzing, 

 Tab. Phyc, Vol. IX, PI. 38, resemble in habit two extreme forms, 

 of this species, but both of them, as well as Dictyota Binghamiana, 

 appear to be true Dictyotas, the internal layer never haying more 

 than one series of cells. Young plants of Dilophus ftabellaiits have 

 the same structure, but as the plant becomes older, the margin thick- 

 ens, the large cells dividing by partitions parallel to the surface of 

 the frond, for a greater or less distance from the margin, and at the 

 same time the cortical layer often divides in the same manner. In 

 the specimens examined this structure has seemed commonest in the 

 antheridial plants, but this may be merely accidental. 



It is by no means impossible that this species may have passed under 

 the name of Dictyota Binghamiana or of Dictyota Kunthii, with which 

 Dictyota Binghamiana was formerly identified. Older plants of 

 Dilophus flabellatus resemble the other species very much in habit, 

 and the Dilophus structure is to be seen only by careful sectioning. 

 It is less developed than in other Dilophus species, and our plant is in 

 some sense a link between the two genera. Its place would be in the 

 section Marginatae with Dilophus marginatus J. Ag., which also has 

 the greater part of the frond of a single series of interior cells, but whose 

 frond, however, is not stupose, but is attached by a growth of rhizoids. 

 On boulders near low water mark, La JoUa, California, October, 1899 

 and 1900. Mrs. E. Snyder. 



1133. Fucus VESicuLOSUS L. forma limicola, n. f. A very 

 slender form, light yellowish brown when growing, seldom having 

 vesicles, and seldom reaching a length of two decimeters. The com- 



