SPHJJKOCOCCOIDE^. 135 



strong midrib, and transverse veins ; as the frond grows 

 larger, the first-formed leaf becomes more deeply cleft, till 

 the cutting reaches the midrib ; the membrane of the older 

 part decays, and the denuded midribs are again thickened 

 into imperfectly-formed stems and branches, from the sides 

 and top of which spring numerous leaves, similar in form to 

 the original. Spores in hemispherical conceptacles, which 

 are formed from the substance of the midrib, or of one of 

 the transverse veins ; tetraspores in sori, which are gene- 

 rally lodged in minute marginal leaflets. 



This is one of the handsomest species of this genus, and 

 in form and general appearance resembles a land-plant 

 more nearly than almost any other of our native Sea- 

 weeds. In consequence of this resemblance, it is some- 

 times called the " Oak -leaf Delesseria." The frond varies 

 much in size. In deep-water specimens it is frequently 

 very narrow, and terminates in long, vine-like tendrils. 

 On the coast of North Devon, at Lynton, towards the 

 end of autumn, I found large quantities of very luxuriant 

 specimens cast on shore, — some attached to the stems 

 of Laminaria digitata, in company with Nitophyllum 

 laceratum, Rhodymenia palmata, and D. alata, some 

 in large detached masses. I have also found it in the 

 Channel Islands, and other localities. This plant is 

 perennial, and in perfection in summer and autumn. 



Delesseria alata. The winged Delesseria. 



"Fronds four to eight inches high, forked, much branched ; 

 branches gradually narrower towards the tips, consisting of 

 a strong midrib or stem, bordered by a flat, wing-like lamina, 

 varying from a line to a quarter, or sometimes nearly half 

 an inch in width ; every part of the membrane is furnished 

 with opposite, patent veinlets, connecting the midrib with 



