368 THE SEA SHORE 



sea weeds, with irregularly cleft membranaceous fronds, either vein- 

 less, or with a few indistinctly visible veins only at the base. The 

 spores are in rounded sessile conceptacles scattered on the surface of 

 the frond ; and the tetraspores occur in clusters similarly scattered. 



One of the species N. laceratumso called from the torn and 

 jagged appearance of the frond, is represented on Plate VII. The 

 fronds are attached to a disc-like root, and are very variable in 

 form, being sometimes so narrow as to appear almost threadlike. 

 The plant grows on rocks and large weeds in the lower rock pools 

 and in deep water. In the same genus we have N. pwnctatum, 

 with broad pink fronds, dotted all over with spore-conceptacles and 

 dark-red clusters of tetraspores ; also a few other less common 

 species that are seldom seen except after storms, as they grow 

 almost exclusively in deep water. 



The genus Delesseria contains some beautiful rose-coloured and 

 reddish-brown weeds with delicate, leaf-like, symmetrical fronds, 

 each of which has a darker midrib from which issue transverse 

 veins. The spores are arranged like minute necklaces, and are 

 contained in sessile conceptacles either on the midrib of the frond 

 or on leaflets that grow from the midrib. The tetraspores are in 

 clusters which are scattered over the frond or on its leaflets. The 

 algae of this genus are seldom found growing between the tide- 

 marks, as they generally thrive in deep water, but splendid specimens 

 are often washed up on the beach during storms, especially on the 

 south and south-west coasts. 



FIG. 252. Delesseria alata FIG. 253. Delesseria hypoglossum 



Among these we may specially mention D. alata, known 

 popularly as the Winged Delesseria, with a dark-red, forked frond, 

 consisting of a strong midrib, bordered by a wing-like lamina of very 

 variable width, supported by opposite veins. In this species the 

 clusters of tetraspores are arranged on each side of the midrib or 



