PADINA. 37 



a spreading mass of matted threads. Fronds tufted, 4 12 inches high, 

 about half an inch wide, several times dichotomous, with a strong, percur- 

 rent midrib ; segments linear, mostly obtuse, sometimes acute, the margin 

 quite entire; surface dotted with tufts of white hairs issuing from minute 

 pores. Along the midrib are frequently found minute, oval, fleshy protu- 

 berances or buds, from which new branches frequently spring, so that the 

 frond often appears as if proliferous. Fructification of two kinds, on dis- 

 tinct individuals: 1st, oblong spots of spores, often confluent, arranged 

 along each side of the midrib "; 2nd, large oval spores, scattered irregularly 

 over the surface of the frond ; these were discovered by Mrs. Griffiths, in 

 August, 1828. The same accomplished lady has also observed a curious 

 state of frond, probably connected in some manner with fructification, 

 where the membrane is marked, in the portion usually occupied by spores, 

 with brown, wavy, map-like lines, inclosing spaces which are usually more 

 transparent than the rest of the frond. Substance of the membrane thin, 

 somewhat rigid, not adhering to paper in drying, tearing with facility in 

 an oblique direction toward the midrib, the cellules of which it is composed 

 particularly large. Colour a brownish olive. Smell, when fresh gathered, 

 very powerful and offensive. 



III. PADINA. Adans. [Plate 6, C.] 



Root coated with woolly fibres. Frond flat, ribless, fan- 

 shaped, marked at regular distances with concentric lines, 

 fringed with articulated filaments ; the apex involute. Fruc- 

 tification : linear, concentric sori, bursting through the cuti- 

 cle of the upper surface of the frond, consisting, at maturity, 

 of numerous obovate spores, fixed by their bases; each spore 

 containing four sporules. Name, invented by Adanson, who 

 has not explained its meaning. 



1. P. Pavonia, L. ; frond wedge-shaped at base, erect, 

 broadly fan-shaped, entire or deeply cleft, powdery on the 

 outer surface, and marked with numerous concentric lines, 

 the margin revolute and fringed. Grev. Alg. Brit. p. 62, t. 

 10 ; Hook. Br. Fl. ii. p. 281 ; Wyatt, Alg. Danm. No. 11 ; 

 E. Bot. t. 1276 ; Harv. Phyc. Brit. t. xci. 



On rocks in shallow tide- pools, at half-tide level. Along the extreme 

 southern shores of England in several places, rare. Annual. Summer 

 and autumn. Fronds tufted, 2 5 inches high, stipitate or sessile, broadly 

 fan-shaped or reniform, sometimes entire, sometimes repeatedly and deeply 

 cleft ; the segments all fan-shaped. The whole frond is marked with nu- 

 merous concentric zones, one or two lines apart, and mostly covered with 

 a whitish powdery substance on the under-side. The substance in the 

 lower part is somewhat leathery and opaque ; above it is delicately mem- 

 branous and transparent. The margin, which always preserves its circular 

 outline, is rolled backwards, and fringed with extremely delicate, reddish- 

 brown filaments. The spores are produced in lines along the concentric 

 zones, originating beneath the epidermis of the frond, through which they 



