136 COLLINS AND HEBVET. 



Callithamnion Lyngbye. 



1. Branching distichous, pinnate. 2. 



1. Branching radial or dichotomous. 3. 



2. Little cortication, ceDs long, ultimate ramuU long, slender. 



4. C. roseum. 



2. Much cortication, cells short, pinnae decompound, ultimate ramuli, 



short, stout. 5. C. Hookeri. 



3. Branching alternate throughout. 1. C. byssoideum. 



3. Branching at least in part dichotomous. 4. 



4. Ultimate divisions long, slender. 6. C. cordatum. 



4. Ultimate divisions shorter and stouter. 5. 



5. Alternate branching usually confined to axis and branches of first order, 



otherwise dichotomous. 3. C. HaUiae. 



5. Only smaller divisions dichotomous; distance very short between forkings. 



2. C. corymbosum. 



1. C. BYSSOIDEUM Arnott var. jamaicense Collins, 1901, p. 258; 

 P. B.-A., No. 2045. Gravelly Bay, Jan., Feb., March, Oct., Hervey; 

 April, Aug., Collins. Growing in dense patches, not over 3 cm. high, 

 just belov7 low water mark, in a small cave. In the water it shows 

 a peculiar bluish iridescence, like the bloom on a plum. 



2. C. coBYMBOSUM (Eng. Bot.) Lyngbye, 1819, p. 125, PI. 

 XXXVIII. C; Harvey, 1846-51, PL CCLXXII; Conferva corymbosa 

 Eng. Bot., 1811, PI. MMCCCLII. Washed ashore. Cooper's Island, 

 Feb., Farlow; on Wrightiella Blodgeitii, Harris Bay, April, Collins. 

 In both cases with abundant tetraspores. 



3. C. Halliae Collins in P. B.-A., No. 698; 1906, p. Ill ; P. B.-A., 

 No. 1896. Outlet of Harrington Sound, Jan., Feb., March., Hervey, 

 large and handsome plants; tetraspores in Jan., no other fruit; 

 Burchell's Cove, Feb., large rich purple patches on bottom in shallow 

 water, Hervey; shore of Agar's Island, Dec, Collins. 



4. C. boseum (Roth) Harvey in Hooker, 1833, p. 341; Harvey, 

 1846-51, PL CCXXX; Ceramium roseum Roth, 1798, p. 46. On 

 Codium, near Causeway, Feb., Hervey, with tetraspores. The plants 

 are attached to the Codium by a dense mass of slender filaments with 

 red protoplasts, penetrating deeply the tissue of the host. They are 

 continuations of the descending growths from the bases of the branches, 

 which cover the lower part of the axis, as a cortex. 



5. C. HooKEBi (Dillw.) Agardh, 1828, p. 178; Harvey, 1846-51, 

 PL CCLXXIX; P. B.-A., No. 2046; Conferva Hookeri Dillwyn, 

 1809, PL CVI. Kemp, ag C. spongiosum. Pink Beach, Jan., Feb., 



