506 Dr. Greville on some new species of Sargassum. 



less, ill breadth, attenuated below into a capillary footstalk ; tbe 

 margin so tinely toothed as to appear spinulose under a lens. 

 There is a faint nerve, and notwithstanding the small space, 

 scattered pores on each side. Vesicles spherical, about a line 

 in diameter, on short filiform stalks, and found either at the 

 base of the small branches or accompanying the racemes. Re- 

 ceptacles axillary, and occasionally terminal, cylindraceous, linear- 

 clubshaped, smooth, a line or more long, forming a lax raceme 

 with 2—5 branches, sometimes solitary. Colou)- pale reddish 

 brown. Substance between cartilaginous and membranaceous. 



As I do not possess an authentic specimen of Sargassum an- 

 gustifolium, and as my copy of Tiu-ner's ' Historia Fucorum ' is 

 not at hand, I can only consult the character and description of 

 that plant given by Agardh. And I find there so much that 

 acjrecs with the Alga I have now before me, as to make me very 

 doubtful whether the latter be really distinct. At the same time 

 there are considerable discrepancies. No reference is made to 

 the cauline leaves of my plant, which are very conspicuous. The 

 leaves on the branches, which resemble those of -S. angustifolium 

 in their extreme narrowness, are not sessile as described by 

 Agardli, but pass insensibly into long and very slender footstalks. 

 The vesicles are not mucronate, nor are their little stalks dilated. 

 Lastly, the receptacles are not " subsolitaria," but in racemes of 

 several branches, and instead of being linear -lanceolate, are hueai*- 

 clavate, obtuse and rounded at the apex. Under these circum- 

 stances I have thought it best to separate it in the meantime, 

 and to a;ive a figure which mav assist in its ultimate determiua- 



tion. 



EXPLANATION OF PLATE XL 



Sargassum gracih. 

 Fig. 1. Summit of a branch. 



— 2. Receptacles and vesicle. 



— 3. Receptacle crowned with a tuft of large semifoliaceous teeth. 



2 S: 3 magnified. 



Sargassum leptophgllum. 

 Fig. 1. A small branch. 



— 2. Leaves on very short young shoots, springing from the root. 



— 3. A leaf from the branches, with raceme of receptacles and vesicles. 



— 4. Raceme. 



— 5. Vesicles. 



— 6. Do. with long foliaceous stalks. * 



— 7. One of the same. 3, 4 and 7 magnified. 



Sargassum yiexil^. 

 Fig. 1. Summit of a branch. 



— 2. Cauline leaf. 



— 3. Leaves on very short young shoots, springing from the root. 



— 4. Portion of a branch from near the summit of the frond, with racemes. 



The last nia£rinfied. 



