Ser. MELANOSPERMEiE. Fam. Dictyotea. 



Plate CTII. 



DICTYOTA DICHOTOMA, Lamour. 



Gen. Char. Root coated with woolly fibres. Frond flat, membranaceous, 

 ribless, reticulate, dichotomous or irregularly cleft. Fructification, 

 scattered clusters of spores formed beneath the cuticle, through which 

 they finally burst; or, on distinct plants, solitary spores irregularly 

 dispersed over the surface. Dictyota (Lamx.) — from 8lktvov, a net; 

 because the surface is reticulated. 



Dictyota dichotoma ; frond regularly dichotomous, linear; segments cu- 

 neate at the base, erect or erecto-patent, gradually narrower towards 

 the apices, axils rounded. 



Dictyota dichotoma, Lamour. Ess. p. 58. Grev. Alg. Brit. p. 57. t. 10. Hook. 

 Br. Fl. vol. ii. p. 280. Harv. in Mack. Fl. Rib. part 3. p. 177. Wyatt. Alg. 

 Damn. No. 10. Harv. Man. p. 32. Buby. Bot. Gall. p. 954. Menegh. Alg. 

 ItaL and Balm. p. 224. Endl. 3rd. Suppl. p. 24. Mont. Fl. Alg. p. 30. 



Zonaria dichotoma, Ag. Sp. Alg. vol. i. p. 133. Ag. Syst. p. 266. Hook. Fl. 

 Scot. vol. ii. p. 90. Grev. Fl. Edin. p. 297. 



Dichophyllium vulgare, Kiitz. Phyc. Gen. p. 337. t. 22. II. f. 1-4. 



Dichophyllium dichotomum, Kiitz. 1. c. p. 338. 



Haliseris dichotoma, Spreng. Syst. Veg. vol. 4. p. 328. 



Ulva dichotoma, Huds. Fl. Ang. Ed. vol. ii. p. 568. (ed. vol. i. p. 476.), 

 Light/. Fl. Scot. p. 975. t. 34. With. vol. iv. p. 124. Eng. Bot. t. 774. 

 Lyngb. Hyd. Ban. p. 31. t. 6. C. 



Var. j3. intricata ; frond very narrow, much branched, twisted and entan- 

 gled, Grev. 



Dictyota dichotoma, /3. intricata, Grev. Alg. Brit. p. 58. Menegh. Alg. ItaL 

 and Balm. p. 227. 



Dictyota implexa, Lamx. I. c. J. Ag. Alg. Medit. p. 37. Mont. Fl. Alg. p. 30. 



Dichophyllium implexum, Kiitz. Phyc. Gen. p. 338. 



Hab. Parasitical on various Algse ; also growing on rocks and stones in 

 tide-pools near low- water mark, and at a greater depth. Annual. 

 Summer. Both varieties common on the British Coasts. 



Geogr. Distr. Abundant throughout the Atlantic Ocean, extending from the 

 shores of Norway to the tropic. Southern Ocean, Western Shores of South 

 America ; Cape of good Hope ; New Zealand. 



Descr. Root small, coated with fibres. Fronds several from the same base, from 

 three to twelve inches in length, from \ to \ an inch in breadth, cuneate at 

 base, afterwards nearly linear, very ni;iii\ times divided in a regularly 

 dichotomous manner ; segments generally very erect, W itli narrow interstices, 

 occasionally more or less spreading. Substance delicately membranaceous, 

 Colour olivaceous towards the tips. Fructification ; oval clusters of Bpores, 



2 c 



