318 
2. THALASSIOPHYTAE. PI cell. aph. 
C. Thallus with a continued fibrous axis j bark chalklike , 
jointed . Corallideae. 
Thallus forked; joints cylindrical Jania. 39. 
Thallus three-forked ; joints wedgelike Corallina. 40. 
D. Thallus continutus green or reddish ; fibres parallel , 
diverging from the base; lark chalklike or hairy . Zonarideae. 
Thallus ribless, fanshaped Zonaria. 41. 
Thallus ribless, forked . . . . Dictyota. 42. 
Thallus ribbed, forked Dictyopteris. 43. 
E. Thallus continuous , cellular , green becoming luhite ; 
bark smooth ; sporidia scattered , immersed. Ulvoideae. 
Thallus compressed ; sporidia prominent 
Asperococcus. 44. 
Thallus membranaceous, flat; sporid. immersed Ulya. 45. 
Thallus tubular ; sporidia immersed Scytosiphon. 46. 
Thallus threadlike, solid Palmella. 47. 
Thallus flat, fleshy Merrettia. 48. 
Thalli globular or ovate, aggregated Olivia. 49. 
F. Thallus continuous , gelatinous, fleshy, cellular ; spori- 
dia in many immersed beaded filaments. Linkidese. 
Thallus long; sporidia elliptic Carrodorus. 5J. 
Thallus bullated ; sporidia globular Nostoc. 50. 
G. Thallus continuous , gelatinous , cellular , smooth, olive 
becoming black ; spoiidia scattered , immersed. Alcyonidese. 
Cells 6-edral, long ; marine Alcyonidium. 52. 
Cells long, regular, radiating Ephidatia. 53. 
Cells irregular ; marsh Spongilla. 54. 
H. Thallus continuous , spongy , gelatinous, formed of in- 
terlaced fibres or spicula yellowish ; sporidia scattered, im- 
mersed. Spongidiae. 
Thallus branched, solid; fibres entangled .. Tupha. 55. 
Thallus tubular y fibres entangled Scypha. 56. 
Thallus not branched ; fibres entangled . . Spqngia. 57. 
Thallus orbicular ; fibres radiated Tethya. 58. 
