256 



NIGELLASTRUM NiGRUM, OJcen, Lehrb. Nat. 93. 

 DIPHASIA NIGRA, Agass. N. H. U. S. iv. 355. 



Plate LII. 



SHOOTS pinnate, somewhat lanceolate, deep red or pink when 

 living, drying black or reddish brown; STEMS straight, 

 tapering towards the tip, compressed, delicately serrated ; 

 pinnce simple, alternate or sometimes opposite, not 

 constricted below the calycles, much attenuated towards 

 the base, often greatly elongated ; HYDROTHEC^E subal- 

 ternate, or sometimes opposite, small, crowded, tubulous, 

 adherent, slightly everted at the top, with a wide, even 

 aperture ; GONOTHEC^E (male) ovate, tapering to a blunt 

 point below, with a number of short denticles at the top, 

 round the central papillary aperture; (female) ample, 

 subsessile, smooth and varnished, obovate, divided by longi- 

 tudinal lines, which meet at the apex, into four lobes. 



THE Sertularia pinnata and S. nigra of Pallas must be 

 united as one species, the only differences between them 

 being dependent upon sex. The former specific name, 

 which Pallas applied to the male, and which is preferable 

 in itself, may be retained. 



The shoots, which attain a height of 6 inches or up- 

 wards, spring from the midst of a twisted and tangled 

 mass of fibres, which sometimes involves the lower part 

 of the stem for a considerable distance*. A sheaf of many 

 plumes is often bound together at the base in this way. 

 The species varies in habit. In some cases the shoots are 

 plumous in form, elongate and slender; in others the 

 pinnse are enormously produced, giving a breadth of as 

 much as 3 inches. The pinnae taper off very finely to- 

 wards the point of origin, becoming suddenly thicker 

 above it, and continuing of equal width to the extremity. 

 There is no constriction below the calycles as in all the 



* Tubi intestinuliformes, implexi, usque ad pinnarum originem sissurgen- 

 tes." Pallas. 



