Var. 8. gracilis; very slender, barren, the internodes fusiform, tapering at 

 each end. 



HoRMOsiRA gracilis, Kiltz. Sp. Alg. v. 2. p. 586. 

 Hab. Littoral rocks, from near high-water mark to the laminarian zone, 

 along the south and south-east coasts of New Holland. Abundant. 

 Geogr. Distr. Australia. Tasmania. New Zealand. 



Descr. Frond from two inches to two or three feet or more in length, varying 

 in dimensions according to the depth of water at which it grows, dichoto- 

 raously or irregularly branched, consisting of a series of inflated internodes 

 and filiform nodes ; the internodes partaking of the charact(;rs of vesicles 

 and receptacles. Leaves none. Vesicated internodes very variable in size 

 and shape, spherical, oblong, ovoid, obconic, obovate, or somewhat cupped ; 

 occasionally prolonged into cyUnders 2-3 inches long ; the centre hollow, 

 and more or less inflated, with a few central threads ; the periphery coria- 

 ceous, cellular, and when fertile (as is usually the case) filled with spore- 

 cavities of the usual fucoid structure. Colour olivaceous or bottle-green, 

 becoming black in drying. Substance rigid. 



Whoever has seen and carefully studied this plant on its na- 

 tive coasts will, if I mistake not, fully agree with me in redu- 

 cing to one species the several synonyms enumerated, and the 

 several forms represented on our Plate. The differences in size 

 and shape of the vesicles seem to result merely from local causes ; 

 either from the depth of water at which the specimen was grown, 

 or from exposure to open sea, or shelter in enclosed harbours. 

 The form called BillarcUeri grows in deep water ; Banksii in 

 sheltered harbours ; and Sieberi and gracilis on exposed tidal 

 rocks or in small rock-pools. Intermediate forms between all 

 the varieties may readily be found. But, in truth, this species 

 does not present nearly so many variations as the Fucus vesicu- 

 losus of the northern hemisphere. 



Fig. 1. HoRMOsiRA Banksii, var. 5?7^art??m. 2. N ax. Banksii. 3, Var. i?i7- 

 lardieri, with cylindrical extremities. 4. Var. Sieberi. 5 and 6. Var. gra- 

 cilis : — all of the natural size. 



