PTILOTA. 159 



V. GRIFFITHSIA. Frond articulated, dichotomous, or 



clothed with whorled, dichotomous raraelli, rose-red. 

 Favellce involucrated, sessile or pedunculate. Tetra- 

 spores sessile, on whorled raraelli. [Plate 23, B.] 



VI. WRANGELIA. Frond articulated, pinnate. Favella 

 terminal, involucrated, containing tufts of pear-shaped 

 spores. Tetraspores sessile, scattered in the ramelli. 

 [Plate 23, D.] 



VII. SEIROSPORA. Frond articulated. Tetraspores dis- 

 posed in terminal, moniliform strings. [Plate 23, C.] 



VIII. CALLITHAMNION. Frond, at least the branches and 

 ramuli, articulated, mostly pinnated. Favellce termi- 

 nal or lateral, sessile, without involucre (except in C. 

 Turneri). Tetraspores sessile or pedicellate, scattered. 

 [Plate 23, A.] 



I. PTILOTA. Ag. [Plate 22, A.] 



Frond inarticulate, linear, compressed or flat, distichous, 

 pectinato-pinnate ; the pinnules sometimes articulate. Fruc- 

 tification : 1, roundish, clustered favellce surrounded by an 

 involucre of short ramuli ; 2, tetraspores attached to or im- 

 mersed in the ultimate pinnules. Name, TnfouTos, pinnated ; 

 from the delicately pinnated frond. 



1. P. plumosa, L. ; frond cartilaginous, decompound ; se- 

 condary branches bi-tripinnate, elongate ; pinnae and pin- 

 nules exactly opposite, the latter subulate, cellular, traversed 

 by a narrow, immersed, articulated filament ; tetraspores on 

 short pedicels, fringing the margin of the pinnules ; favellae 

 pedunculate, with an involucre of 6 8 subulate ramuli. 

 Harv. Phyc. Brit. t. Ixxx. ; Grev. Ala. Brit. p. 155, t. 16 ; 

 Hook. Br. Fl. ii. p. 307. Fucus plumosus, E. Bot. t. 1308. 



On the stalks of Laminariee. Perennial. Summer and autumn. 

 Northern and western coasts of Great Britain and Ireland. Fronds 3 14 

 inches long, much and irregularly branched ; branches from a quarter to 

 half a line in width, attenuated upwards, patent, opposite or alternate, 

 closely set with opposite, distichous, pinnated, lanceolate ramuli, from one 

 to four lines in length, the pinnules acute, narrow- lanceolate, simple, or, 

 in luxuriant specimens, again pinnated. Favellee clustered, surrounded by 



