388 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



brane at the tip somewhat thickened at the central part and 

 projecting inwards. Alaska to Vancouver. 



Nearest allied to C. mamillosum Harv., but that species has 

 balloon-shaped utricles, 1-2 mm. diam. 



4. C. REPENS Crouan in Vickers, 1905, p. 56; 1908, p. 23, 

 PI. XXIX ; C. tenue var. repens Crouan in Maze and Schramm, 

 1870-77, p. 107. Branching like that of C. tomcntosum but 

 branches prostrate and entangled, attaching themselves to the 

 substratum by short special branches ; utricles 150-300 p. diam. 

 On rocks at low tide. Barbados, Guadeloupe. 



5. C. TOMENTOSUM (Huds.) Stackhouse, 1795, p. 21, PL 

 VII; Harvey, 1846-51, PI. XCIII ; 1858, p. 29, in part ; Vick- 

 ers, 1908, p. 22, PL XXVI; P. B.-A/, No. 168. Frond erect, 

 cylindrical, dichotomously branched, more or less fastigiate, 

 surface smooth and soft; utricles obovate-clavate, 100-150 p., 

 rarely 200 yu. diam., 3-6 diam. long., apex obtuse, unarmed. 

 N. C. to Fla.; W. I. Europe, Asia, Africa, Occanica. 



A cosmopolitan species, but many forms once included here 

 have been removed, and it may be that a careful comparison 

 would considerably reduce the number of localities for C. tomcn- 

 tosum. The principal distinctions from similar species are found 

 in the cylindrical frond, and the unarmed tips of the utricles. 



6. C. ISTHMOCLADUM Vickers, 1905, p. 57; 1908, p. 23, PL 

 XXVIII. Frond dichotomously branched, the branches usu- 

 ally constricted at the base ; utricles 200-300 p. diam. Barba- 

 dos, Guadeloupe. 



7. C. ELONGATUM Agardh, 1822, p. 454; Vickers, 1908, p. 

 22, PI. XXVII; P. B.-A., No. 627. Frond dichotomously 

 branched, often much elongate, younger divisions terete, older 

 compressed, especially below the dichotomies, being there dis- 

 tinctly cuneate ; utricles obovate-clavate, 300-400 ju, diam., 5-6 

 times as long as the greatest diam. N. C. to Fla., W. I. 



Europe, Africa, So. America. 



The younger plants resemble C. tomentosum, but the flatten- 

 ing is marked in older plants ; in some cases all parts except 

 the younger tips are quite broadly cuneate. 



8. C. L,INDENBERGII Binder in Kiitzing, 1856, p. 34, PL 

 XCVII ; P. B.-A., No. 628. Frond di- polychotomous, com- 

 pressed or flat in all parts, segments cuneate, terminal linear- 

 lanceolate ; utricles clavate, 80-150^ diam., 3-4 times as long 

 as the greatest diam. Cal. Africa. 



The fronds in this species are sometimes triangular or reni- 



