282 Minnesota Algae 



land. 39. pi. I. f. 2. 1881. Pike. Check List of Marine Algae. Bull. Torr. 

 Bot. Club. 13: 106. 1886. Collins. Marine Algae of Nantucket. 5. 1888; 

 Algae from Atlantic City, N. J. Bull. Torr. Bot. Club. 15: 310. 1888. Mar- 

 tindale. Marine Algae of the New Jersey Coast and Adjacent Waters of 

 Staten Island. Mem. Torr. Bot. Club, i: 91. 1889. WoUe and Martindale. 

 Algae. Britton's Catalogue of Plants found in New Jersey. Geol. Surv. 

 N. J. 2: 603. 1889. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 

 4. no. 156. 1896. Collins. Preliminary Lists of New England Plants. — V. 

 Marine Algae. Rhodora. 2: 42. 1900; Phycological Notes of the late Isaac 

 Holden. — II. Rhodora. 7: 224. 1905. 



Plate XIX. fig. s. 



Plant mass green, becoming brown or black, showing dark purple tints 

 v.'hen dried; filaments decumbent at the base, up to .5 mm. in length, 

 crowded; sheaths close, transparent, sometimes yellowish, scarcely distinct; 

 trichomes 7-9 mic. in diameter, produced at the apex into a very long, thin 

 hair; cells shorter than their diameter; cell contents blue-green or green- 

 ish violet. 



New England. Very common on rocks and on other algae, forming 

 dark green spots scarcely raised above the substance on which it is grow- 

 ing. (Farlow). Massachusetts. On Fucus vesiculosus at half 

 tide. Cuttyhunk. August 1894. (Setchell). On shells. Polpis. (Collins). 

 Connecticut. On stones. Charles Island. September. (Holden). New 

 York. Wet rocks. Portage. (Wolle). On shells at and below low water 

 mark. Cold Spring Harbor. August 1895. (Johnson). Shores of Long Island. 

 On Fucus. Fort Hamilton, Jamaica Bay. (Pike). New Jersey. On 

 stones and old oyster shells. Atlantic City. (Morse, Martindale). 



Var. fissurata Bornet and Flahault. 1. c. 345. De Toni. 1. c. 647. 



Setchell and Gardner. Algae of Northwestern America. Univ. Calif. Pub. 

 Bot. i: 198. 1903. 



Plant mass zonate; filaments branched, closely cohering; especially 

 rock-loving. 



Alaska. On stones. Captains Bay, Unalaska. (Lawson). 



517. Isactis centrifuga Bornet in Collins. Notes on Algae. — III. Rhodora. 

 3: 136. 1901. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 

 16. no. 757. 1900. De Toni. Syll. Algar. 5: 647. 1907. 



Plant mass up to 4 cm. in diameter, the growth marginal, the central 

 portion of the mass becoming detached from the substratum and rounding 

 upwards, while the margin remains closely attached, dark green or nearly 

 black; filaments 8-12 mic. in diameter, slightly swollen at base, reaching a 

 length of a millimeter; sheaths firm, usually translucent, sometimes brown- 

 ish and opaque; trichomes 8-10 mic. in diameter; cells one-third to one- 

 half as long as wide; heterocysts basal, spherical or depressed, rarely in- 

 tercalary and spherical or elongate. 



Rhode Island. On soft crumbling rocks, at low water mark. Ochre 

 Point, Newport. May, June 1900. (Collins). 



