74 ERYTHEA. 



and five inches long, and does not often attain a length of more 

 than eight inches. 



Our species may be distinguished from D. polypodioides by its 

 dark color, its denser substance, and by the fact that the dichotomies 

 are more closely arranged and that instead of having long, slender, 

 and more or less tapering ultimate divisions, they are short, blunt, 

 and broader than the frond below. In color and substance 

 D. zonarioided approaches more nearly the Japanese alga collected 

 by C. Wright during the north Pacific expedition under Ringgold 

 and Rodgers to which Harvey gave the name of Halkeris poly- 

 jjodioides var. crispatula, although the name does not appear in his 

 account of the algse of that expedition, Proc. Am. Acad., Arts & 

 Sd. IV, 327, 1859. This form has recently been described jjy 

 Holmes under the name of Didyojjteris undulata, Jour. Linn. Soc. 

 XXXI, 251, PI. 8, fig. 1, 1896. This plate gives a correct repre- 

 sentation of the habit of Harvey's var. crispatula, of which I have 

 seen all the specimens collected by AVright. They were all 

 remarkably alike and showed no variation of habit and, at first 

 sight, their very regular crisped laminae do not suggest at all our 

 Californian alga. In a few rather poor specimens of the latter, the 

 laminae are somewhat crisped, but in by far the majority of cases 

 one is struck by the constantly incised fronds with few if any 

 undulations. It might be supposed that the incisions in one plant 

 were in fact ruptures of the folds of a crisped, in which case younger 

 specimens should show the folds. But, on the contrary, the younger 

 and fresher specimens are not crisped at all. Certainly neither 

 Wright specimens nor the figure quoted represents the typical form 

 of D. zonarioides, and, unless a farther study of the Japanese 

 species shows that it varies towards the tyjiical form of our own 

 species, the two must be kept distinct. 



Spermothamnion Snyderae Farlow. Exs. Phycotheca Bo- 

 reali- Americana, No. 598. 



Fronds csespitose, filamentous, monosiphonous, primary filaments, 

 procumbent rooting, branches vertical, monopodial bearing below a 

 few long simple ramuli and above more numerous, shorter secund 

 ramuli which are 2-3 times secundly cymose. Tetrasporangia 

 terminal on the ultimate secund ramuli, at first tripartite, becoming 



