160 PTILOTA — MICROCLADIA. 



an involucre, terminating the ultimate pinnules, the involucre composed 

 of several subulate ramuli. Substance cartilaginous. Colour a fine 

 dark red. 



2. P. sericea, Gmel. ; frond flaccid, excessively branched ; 

 secondary branches bi-tripinnate ; pinnae and pinnules ex- 

 actly opposite, the latter linear, composed of a single row of 

 cells ; tetraspores on short processes of the pinnules ; fa- 

 vellae pedunculate, binate, naked, or surrounded with a few 

 irregular ramuli. Harv. Pltyc. Brit. t. cxci. P. jjlumosa, 

 &. capillaris, Harv. in Man. Ed. 1, p. 84 ; Wyatt, Alg. 

 Damn. No. 77. 



On perpendicular rocks, between tide-marks, common ; rarely on the 

 stems of Fucus serratus. Perennial. Summer and autumn. All round 

 the British coast. — Fronds tufted, 2 — 6 inches long, excessively branched, 

 sometimes very dense, flaccid and soft to the touch, repeatedly pinnate. 

 Ultimate pinnules very closely set, distinctly articulated, composed of a 

 single row of coloured cells. Colour rarely a brilliant, usually a dull 

 brownish red. A smaller and more delicate plant than the preceding, of 

 much darker colour and more flaccid substance, and readily distinguished 

 by the articulated pinnules. This species is the only Piilota found on the 

 south coast of England. 



II. MiCROCLADiA. Grev. [Plate 22, B.] 



Frond filiform, compressed, distichously branched, tra- 

 versed by a wide articulated tube surrounded by numerous, 

 large, coloured, angular, radiating cells, the outer coat formed 

 of minute cells. Frnctijication : 1, sessile, roundish, invo- 

 lucrated favellce ; 2, tetraspores immersed in the ramuli. — 

 Name, f^Mpoi, small, and fcxahg, a branch. 



1. M. (jlandidosa, Soland. Grev. Alg. Brit. p. 99, t. 13; 

 Hook. Br. Fl. ii. p. 293 ; Wyatt, Alg. Damn. No. 68 ; Harv. 

 Phyc. Brit. i. xxix. Fucus glandulosus, E. Bot. t. 2135. 



In the sea, on other Algse ; very rare. Annual. Producing fruit in 

 September and October. South of England, and East coast of Ireland. 

 At Bray, Mr. Sanders; Kingstown, Mr. Andreu-s. — Fronc/s tufted, I or 2 

 inches high, about a quarter of a line in width, compressed, much branched 

 from the base in an alternate or irregularly dichotomous manner, forming 

 roundish fastigiate tufts ; branches distichous, with patent axils, preserving 

 nearly an equal breadth throughout, repeatedly divided, the ultimate ra- 

 muli short, and either subulate or bifid at the apex, in which case the points 

 are forcipate. Under a low power of the microscope the branches appear 

 marked with large, hexagonal, transverse areolae, about three of which 

 form the breadth of the frond, an appearance caused by the large cellules 

 of the central part of the frond being seen through those of the surface, 

 ■which latter, on increasing the magnifying power, are found to be exceed- 

 ingly small and close. Colour a fine rose red. Substance cartilagineo- 



