184 University of California Pnhlications in Botany [Vol. 8 



Brit., vol. 1, 1846, pi. 54 B. Rhizoclonium ripurium var. implexum 

 Rosenvinge, Groenl. Havalg., 1893, p. 915; Saunders, Alg. Harriman 

 Exp., 1901, p. 414; Setchell and Gardner, Alg. N.W. Amer., ]903, 

 p. 222; Collins, Holden and Setchell, Phye. Bor.-Amer, (Exsiec), no. 

 976 ; Collins, Green Alg. N. A., 1909, p. 328. Rhizoclonium riparium 

 Tilden, Amer. Alg. (Exsice.), no. 379 (not of Roth or Kuetzing). 



A plant very similar to Rhizoclonium ripariimi, but destitute of, 

 or provided with very few and simple, rhizoids, is found on the shores 

 of the Pacific Coast of North America. This seems to be the same 

 as the plants from both the European and North American Coasts 

 which have passed under the name of Rhizoclonium riparium var. 

 implexum. The filaments are nearly the same in diameter as those 

 of the preceding, but possibly average slightly smaller. The rhizoidal 

 branches are often entirely wanting and in no case are really abun- 

 dant. When present they alway lack septa and generally are not cut 

 off from the segment from which they arise. The growth is generally 

 more entangled and fleecelike than that of the preceding species. It 

 seems best to us to keep this form, which seemingly has a wider dis- 

 tribution along the Pacific Coast than R. riparium, separate. In 

 adopting the name of R. implexum, we are guided by the descriptions 

 of others. The type specimen of Dillwyn is unknown to us, but this 

 seems to be the plant of Harvey and possibly also of Kuetzing and 

 Rosenvinge. Harvey evidently founded his description on Miss 

 Hutchins's specimen from Bantry Bay which is a topotype, possibly 

 even a cotype of Dillwyn 's species. Harvey and Dillwyn give no 

 measurements of Conferva implexa, but Harvey states that the fila- 

 ments are about two-thirds of the thickness of those of C. tortuosa. 

 The latter is probably 40fi to 70^ in diameter. Kuetzing assigns to 

 his Rhizoclonium implexum a diameter of ^oo'"-/45o''' oi* about 11/x 

 to 12/A, which is very much more slender than the Rhizoclonkim 

 riparium var. implexum, of Rosenvinge which is described as being 

 20/A to 30/x, (or 40/a) in diameter. 



Our plants agree well with no. 142 and even with no. 190 of 

 Wyatt's Algae Danmonienses, issued under the names of C&nferva 

 implexa and C. tortuosa respectively. No. 142 shows no rhizoids 

 while no. 190 shows frequent unseptate rhizoids. The segments in 

 no. 142 vary from 35/* to 45/*, while those of no. 190 vary from 22/^ 

 to 27/x,. They also agree in general with no. 624 of Wittrock and 

 Nordstedt's "Algae aquae dulcis exsiccatae, " distributed under the 

 name of Rhizoclonium riparium f. valid a Foslie. 



