Howe: Phycological studies 491 



are rather difficult to distinguish from Enteromorpha compressa 

 forma simplex Wittr. & Nordst. (Alg. Exsicc. 326), but the two 

 layers of the thallus appear to separate less easily in the upper 

 broader parts, the marginal cells in a cross section are more 

 elongate and more radiately disposed, and the cells in general are 

 more distinctly in lines in the lower parts. No trace of branching 

 has been observed. 



Cladophora MacDougalii sp. nov. 



Rather stout, coarse, and rigid, in strict tufts, dark- or yellow- 

 ish-green, 10-17 cm. high; main filaments 135-310^ in diameter, 

 sparingly dichotomous below the middle of the tufts; branching 

 in median and upper parts lateral, the branches erecto-patent, 

 secund, occasionally alternate, or very rarely opposite, becoming 

 more or less secund-pectinate toward apices, the main axes com- 

 monly excurrent beyond the last lateral branch as rather rigid 

 tapering prolongations 10-40 cells long; the ultimate lateral 

 branchlets 75-1 io/z in diameter, about one half the diameter of 

 the filaments from which they spring, usually 3-7 cells long, in 

 most cases gradually tapering from near the base, subacute or 

 blunt, commonly rather rigid; cells in extreme basal parts 6-15 

 times as long as broad, in median and upper parts 1-4 (mostly 

 i^Ar^A) times as long as broad, usually a little constricted at the 

 septa and appearing quite strongly constricted when dry. [Plate 

 33, figure 7.] 



San Felipe Bay, D. T. MacDougal, Feb. 1904. 



The present species is evidently allied to both Cladophora 

 Hutchinsiae (Dillw.) Kiitz. and to C. ovoidea Kiitzing, but is not 

 satisfactorily identified with either. In size it resembles C. 

 Hutchinsiae (type from Ireland), but it is more rigid and much 

 more strict in habit of growth; dichotomies are rare above the 

 middle of the tuft, while in C. Hutchinsiae they commonly persist 

 almost to the apices; the ultimate lateral branchlets in C. Mac- 

 Dougalii are much more slender than the axes from which they 

 arise, having usually, in their middle parts at least, only half the 

 diameter of the parent filament, while in C. Hutchinsiae the corre- 

 sponding branchlets are as a rule only slightly less stout than the 

 filament from which they spring; in C. MacDougalii ultimate lateral 

 branchlets of I or 2 cells in length are extremely rare, 5 to 7 cells 

 being the prevailing number, while in C. Hutchinsiae branchlets 

 of 1 or 2 cells are very common. 



